Why Is My Computer So Slow? Every Cause & Fix for Windows (2026)

Step 0: Diagnose what is actually slowing your PC

Before you change anything, spend two minutes finding the actual bottleneck. Open Task Manager with Ctrl + Shift + Esc and click the Performance tab. You will see real-time graphs for CPU, Memory, Disk, and Network. The one pegged near 100% while your PC feels slow is usually your culprit.

• CPU at 90–100%: A runaway process is consuming your processor. Switch to the Processes tab, click the CPU column header to sort, and look at what is at the top. Common offenders: antivirus scans, Windows Update, browser with many tabs, or malware.
• Memory at 90–100%: You are running out of RAM. Windows starts using the disk as overflow (paging), which is 50–100x slower than actual RAM. Fix: close apps, or upgrade RAM.
• Disk at 100%: Your drive cannot keep up with read/write demand. This is extremely common on PCs that still use spinning hard drives (HDD). It can also happen when Windows Update is downloading in the background.
• Everything looks fine: The problem might be intermittent, or in the GPU. For GPU issues, check Task Manager's GPU column, or use a free tool like HWiNFO64 for detailed sensor data.

For a deeper look, open Resource Monitor (search for it in Start) — it shows exactly which files each process is reading and writing, which network connections are active, and how RAM is distributed. If you find a specific process you do not recognise consuming resources, search for its exact name online before killing it.

Fix 1: Disable unnecessary startup programs

This is the single most effective fix for slow boot times, and it takes less than two minutes. Every time you install a program — a game launcher, a messaging app, a creative suite — it often adds itself to your startup list without asking. Over a few years, a PC can accumulate 20 to 40 programs all competing to load simultaneously when Windows starts, each consuming RAM before you have even opened a single app yourself.

How to fix it:

1. Press Ctrl + Shift + Esc to open Task Manager.
2. Click the Startup apps tab (in Windows 10, it may be under the More Details view).
3. Click the Startup impact column header to sort by impact — High and Medium entries are the ones costing you boot time.
4. Right-click any entry and select Disable for apps you do not need immediately at login.

Safe to disable: Spotify, Steam, Discord, Epic Games Launcher, OneDrive (if you do not rely on cloud sync), Adobe Updater, Microsoft Teams (if not used for work), any browser update helper.

Leave enabled: Your antivirus or security software, audio drivers (Realtek HD Audio Manager, Sound Blaster), GPU control panels (NVIDIA, AMD), and any VPN that needs to run at login.

Disabling a startup entry does not uninstall or break the app — it simply stops it from launching automatically. You can still open it manually whenever you want. After making changes, do a full restart (not sleep) and compare your boot time. Most users see boot times drop by 30–60 seconds after this step alone.

Fix 2: Free up disk space on your C: drive

Windows requires free space on the system drive to function normally. It uses free space for virtual memory (your RAM overflow), temporary files created during normal operations, Windows Update staging, and system restore points. Once your C: drive drops below 10–15% free, performance degrades noticeably. Below 5% free, the system can become unstable.

Quick wins — no risk of data loss:

• Run Disk Cleanup: Search for "Disk Cleanup" in Start, run it on your C: drive, then click "Clean up system files." This can safely remove old Windows Update files, temporary internet files, and error reports. It is common to recover 5–15 GB this way on a PC that has never had this run.
• Enable Storage Sense: Go to Settings > System > Storage > Storage Sense and turn it on. Configure it to automatically delete temp files and empty the Recycle Bin weekly.
• Clear the Downloads folder: Downloads folders accumulate installers, zip files, and documents that were needed once and forgotten. Sort by size and delete anything you no longer need.

Find hidden space hogs: Install the free tool WinDirStat or use Windows 11's built-in Storage breakdown (Settings > System > Storage). Both show you a visual map of what is consuming space. It is common to find 20–50 GB buried in old game installs, video projects, or software cache folders.

Move large files to external storage: Photos, videos, and archives belong on an external drive or cloud storage, not on your system drive. Windows 11 also supports moving your Documents, Pictures, and Downloads folders to a secondary drive via folder Properties > Location > Move, which keeps your C: drive lean without changing your workflow.

Uninstall unused programs: Go to Settings > Apps > Installed apps, sort by Size, and uninstall games or software you no longer use. Even games you finished years ago can sit taking up 30–80 GB.

Note on third-party cleaners: Tools like CCleaner delete temp files but don't diagnose performance issues. If you're evaluating options, see our comparison of CCleaner alternatives that actually fix slow PCs.

Fix 3: Scan for malware and hidden miners

Malware is more common than most users expect, and modern malicious software is designed to be invisible. You will not see a skull and crossbones — instead you will notice your PC is inexplicably slower, your fan runs constantly, and your Task Manager shows high CPU or disk usage from processes with vague or system-sounding names.

The most resource-intensive category is cryptocurrency miners (cryptojackers). These programs silently use 50–100% of your CPU or GPU to mine digital currency for the attacker. They are particularly common on PCs that have downloaded cracked software or browser extensions from unofficial sources.

How to scan:

1. Open Windows Security (search for it in Start).
2. Go to Virus & threat protection and run a Full scan — not a Quick scan. Full scan checks every file on the drive.
3. Separately, download and run Malwarebytes Free (malwarebytes.com) — it catches a different category of threats (adware, PUPs, browser hijackers) that Windows Defender often misses.

If Task Manager shows a process consuming significant CPU that you do not recognise, right-click it and select Open file location. Legitimate Windows processes live in C:\Windows\System32. A suspicious process living in a temp folder, AppData, or a random user directory is a red flag.

After removing malware, do a full restart. CPU and disk usage typically drop immediately and noticeably.

Fix 4: Update your drivers, especially the GPU driver

Outdated drivers are a silent performance killer. A driver is the software layer between Windows and your hardware — when it is outdated, buggy, or mismatched with the current version of Windows, you pay for it in the form of crashes, freezes, high CPU usage from the driver process itself, and degraded hardware performance.

The most impactful driver to keep current is your graphics (GPU) driver. NVIDIA and AMD both release driver updates every few weeks with performance improvements, bug fixes, and optimisations for new games and software. An outdated GPU driver can cause stuttering, freezing, and general sluggishness even in non-gaming workloads like video playback and browser rendering.

Update GPU driver:

• NVIDIA: Open NVIDIA GeForce Experience, or go to nvidia.com/drivers and enter your GPU model.
• AMD: Open AMD Software: Adrenalin Edition, or go to amd.com/support.
• Intel (integrated graphics): Use Intel Driver & Support Assistant (intel.com/DSA).

Check for driver problems: Open Device Manager (right-click Start > Device Manager) and look for any entry with a yellow warning triangle. These indicate a driver that failed to load or has a known problem. Right-click the entry and select Update driver, or search for the specific hardware model on the manufacturer's website.

Windows Update alone is not enough. Microsoft's driver database lags behind manufacturer releases by weeks or months. Always download GPU and chipset drivers directly from the hardware maker's website for the most current versions. If your PC slowed down right after a Windows Update, you can roll back a driver via Device Manager > right-click the device > Properties > Driver tab > Roll Back Driver.

Fix 5: Restart regularly to clear memory leaks

Many Windows users leave their PC in sleep or hibernate mode for days or weeks at a time without a full restart. While convenient, this allows memory leaks to accumulate. A memory leak happens when a program requests RAM from Windows and then fails to release it when it no longer needs it. Over time, leaked memory adds up until Windows has very little RAM left to work with — even if you have 16 GB installed.

A full restart clears all allocated memory, resets services that may have drifted into a bad state, and applies pending Windows updates that cannot be installed without a reboot. Aim to restart at least once a week.

A note on Fast Startup: Windows 10 and 11 have a feature called Fast Startup that makes the machine boot quicker by saving a partial hibernation snapshot on shutdown. The side effect is that "Shut down" does not fully reset the kernel session. If you are having persistent slowness, try a full Restart (not Shut down) — this bypasses Fast Startup and performs a complete reset. You can also disable Fast Startup permanently via Control Panel > Power Options > Choose what the power buttons do > uncheck Turn on fast startup.

Fix 6: Check your power settings

Windows power plans directly control how aggressively your CPU is allowed to run. In Power saver mode, Windows caps the CPU's maximum frequency — sometimes as low as 50% of its rated speed — to conserve battery or reduce heat. If your PC was set to Power saver mode (this sometimes happens after a Windows update resets settings), everything from web browsing to file operations will feel sluggish.

How to fix it:

1. Open Settings > System > Power & battery (Windows 11) or Control Panel > Power Options (Windows 10).
2. For a desktop or a plugged-in laptop: select Best performance.
3. For a laptop on battery: Balanced is the right default — it lets the CPU boost when needed but saves energy when idle.

If you do not see Best performance as an option, open a Command Prompt as administrator and run: powercfg /duplicatescheme e9a42b02-d5df-448d-aa00-03f14749eb61. This restores the hidden Ultimate Performance plan, which removes all power-saving throttling entirely.

On laptops, also check the manufacturer's power utility — Dell, HP, Lenovo, and ASUS all have their own software that can override Windows power settings with more aggressive throttling than Windows would apply on its own.

Fix 7: Reduce browser and extension bloat

For most people, the web browser is the most RAM-intensive application on the PC — and also the one most overlooked as a cause of system-wide slowness. Chrome and Edge use a multi-process architecture: every tab, every extension, and every plugin runs as its own process. A browser with 15 open tabs and 8 extensions can easily consume 3–5 GB of RAM, leaving very little headroom for anything else.

Check your browser's own resource usage: In Chrome or Edge, press Shift + Esc to open the browser's built-in task manager. You will see a breakdown of memory and CPU usage per tab and per extension. It is often surprising how much a single extension — particularly ad blockers, password managers with heavy sync, or screenshot tools — consumes on its own.

What to do:

• Limit open tabs. Use a tab manager extension (like OneTab) to suspend tabs you are not actively reading.
• Audit your extensions. Go to your browser's Extensions page and remove anything you installed once and forgot about. A good target is 5 or fewer active extensions.
• Enable Memory Saver in Chrome (Settings > Performance) or Sleeping tabs in Edge — both automatically reduce the memory footprint of inactive tabs.
• Make sure hardware acceleration is enabled: Settings > System > Use hardware acceleration when available. This offloads video decoding and rendering to your GPU instead of the CPU.

If the browser itself is slow and sluggish — not just the system — try clearing the browser cache (Ctrl + Shift + Delete) and resetting the browser profile. A corrupted or very large browser profile can cause the browser to stutter when loading pages and searching history.

Fix 8: Check for overheating and thermal throttling

If your PC runs normally when you first turn it on but slows down noticeably after 20–30 minutes of use, overheating is almost certainly the cause. Modern CPUs and GPUs have built-in protection: when they reach a critical temperature threshold (typically 90–100°C for CPUs), they automatically reduce their clock speed to shed heat. This is called thermal throttling, and it can cut performance by 30–70%.

Signs of thermal throttling:

• PC feels fast when cold, then slows down during use
• Fan runs at maximum speed constantly
• The case is hot to the touch, especially near vents
• Games or video editing software slow to a crawl after 10–15 minutes

How to check temperatures: Download HWiNFO64 (free at hwinfo.com) and run it in sensor mode. Look at the CPU Package temperature and GPU temperature. Under moderate load, a CPU running above 85°C is concerning. Above 95°C consistently means you have a cooling problem.

How to fix it:

• Clean the vents and fans: Dust buildup is the most common cause of overheating. On laptops, use a can of compressed air to blow out the vents (bottom and sides). On desktops, open the case and remove dust from all fans and the heatsink. This alone often drops temperatures by 10–20°C.
• Improve airflow: Make sure the PC is not in a cabinet or against a wall where hot air cannot escape. Laptops should be used on hard flat surfaces, not on blankets or pillows that block the intake vents.
• Re-apply thermal paste (advanced): On a PC that is several years old, the thermal paste between the CPU and its cooler may have dried out. Re-applying fresh paste (a $5–10 procedure) can drop temperatures by 5–15°C. This is a straightforward DIY fix on desktops; laptops require more disassembly.
• Elevate the laptop: A $15 laptop stand that lifts the machine and improves airflow under the chassis can meaningfully reduce temperatures.

Fix 9: Manage background Windows services and scheduled tasks

Windows runs dozens of background services automatically, and several of them can cause temporary but dramatic slowdowns at inconvenient times. The most common culprits are Windows Update (which downloads, installs, and indexes updates in the background), Windows Search (which indexes your files when you are trying to use the PC), and antivirus scans scheduled during business hours.

Windows Update: If Task Manager shows svchost.exe or Windows Update consuming significant disk or CPU, it is running an update. You can defer it: Settings > Windows Update > Advanced options > Pause updates for up to 5 weeks. Do not pause indefinitely — security updates are important — but if you are in the middle of something time-sensitive, pausing for a day is reasonable.

SysMain (formerly Superfetch): This service preloads frequently used apps into RAM. On systems with ample RAM and an SSD it provides minimal benefit. On older machines with limited RAM it can cause sustained high disk usage, especially after a restart. You can disable it via Services (search "Services" in Start) > find SysMain > right-click > Stop, then set Startup type to Disabled. Note: only do this if you are experiencing 100% disk usage.

Schedule your antivirus scans: Open your antivirus software and reschedule any full scans to run overnight (2–4 AM) rather than during the day. Full scans can pin the disk at 100% for 30–60 minutes.

Fix 10: Reduce visual effects and animations

Windows 11 in particular runs a rich set of animations, transparency effects, blur effects, and window shadows. On high-end hardware these are essentially free. On older machines — especially those with integrated graphics and limited VRAM — these effects consume measurable GPU and CPU cycles and can make the UI feel sluggish even when the underlying workload is light.

How to reduce visual effects:

1. Press Win + R, type sysdm.cpl, and press Enter.
2. Go to the Advanced tab and click Settings under Performance.
3. Select Adjust for best performance to disable everything, or choose Custom and uncheck: Animate windows when minimising and maximising, Animations in the taskbar, Fade or slide menus into view, Show shadows under mouse pointer, and Smooth-scroll list boxes.

You can also disable the transparency effect separately: Settings > Personalisation > Colours > turn off Transparency effects. On systems with older integrated graphics, disabling transparency alone can make menus and taskbar interactions feel snappier.

Fix 11: Upgrade hardware — only if software fixes fail

If you have worked through every software fix above and the PC is still frustratingly slow, hardware may genuinely be the bottleneck. The good news is that the two most impactful hardware upgrades are relatively affordable and do not require replacing the entire machine.

HDD to SSD — the single biggest upgrade you can make: If your PC uses a traditional spinning hard drive (HDD), switching to a solid-state drive (SSD) is transformative. HDDs deliver sequential read speeds of 80–160 MB/s; budget SSDs deliver 500 MB/s, and NVMe SSDs reach 3,000–7,000 MB/s. In practical terms: boot time goes from 60–90 seconds to under 15 seconds. Apps that took 10 seconds to open take 1–2 seconds. Windows 11 becomes genuinely responsive. A 1 TB SATA SSD costs $50–80 in 2026. You can clone your existing drive to the new SSD using free software (Macrium Reflect Free) without reinstalling Windows.

RAM upgrade: If Task Manager shows Memory consistently above 80% during your normal workload, you need more RAM. Windows 11 with a browser open and a few background apps uses 5–7 GB at idle. With 8 GB total, multitasking becomes painful. Moving to 16 GB eliminates most memory pressure. Before buying, check: (1) how many RAM slots your motherboard has and how many are occupied, (2) what speed and type your motherboard supports (DDR4 vs DDR5), using CPU-Z (free) to get the exact specs.

When a new PC is actually the right answer: If your CPU is more than 8–10 years old (e.g., an Intel Core i5-4xxx or AMD FX series), the RAM is soldered and not upgradeable, and the drive is already an SSD — the hardware itself is the ceiling and a new machine makes more sense than incremental upgrades.

How long will these fixes take?

Frequently asked questions