Computer Repair Guides

Computer troubleshooting knowledge base

Computer Repair Guides

Clear first-step checks for slow computers, startup faults, Windows corruption, storage, memory, overheating, network problems and other common PC and laptop issues.

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Before changing anything

Back up important files where possible. If a hard drive is clicking, disappearing, extremely slow to read, or contains data you cannot replace, stop repeated repair attempts and consider data recovery first.

Choose the symptom

Start with what the computer is doing

These guides cover Windows 10 and Windows 11 unless stated otherwise. Work through the simple checks first, then move to the deeper tests only if the fault remains.

01

Performance

My computer is running extremely slow

A slow computer can come from software, a failing hard drive, too little RAM, overheating, low disk space, malware, or background programs.

Start here

  1. Restart the computer. A full restart clears stuck processes and pending updates.
  2. Open Task Manager with Ctrl + Shift + Esc.
  3. On the Processes tab, check CPU, Memory and Disk usage.
  4. On the Performance tab, check whether the main drive is listed as an HDD or SSD and how much RAM is installed.
  5. Check free space in File Explorer. Windows needs free space for updates, temporary files and virtual memory.

What the readings can mean

  • Disk near 100% for long periods: an old or failing HDD, Windows indexing, updates, antivirus scans, or another program may be saturating the drive.
  • Memory above 80–90% during normal use: the PC may not have enough RAM for the workload.
  • CPU near 100%: check which process is using it. High CPU at idle can point to software, malware, updates or a cooling problem.
  • Everything is slow on an HDD: moving Windows to an SSD can make a major difference on older systems.
Common workshop causes: ageing mechanical hard drives, 4 GB of RAM on modern Windows, failing storage, too many startup programs, damaged Windows files, thermal throttling and malware.
02

Windows repair

Repair corrupted Windows files with DISM and SFC

Use these built-in Microsoft tools when Windows features fail, updates break, system files appear damaged, or the computer behaves strangely after a crash.

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These commands do not erase your personal files.

They repair the Windows component store and protected system files. Save your work first and run them from an Administrator terminal.

Step 1 — Open an Administrator terminal

  1. Right-click the Start button.
  2. Choose Terminal (Admin), Windows PowerShell (Admin) or Command Prompt (Admin).
  3. Approve the User Account Control prompt.

Step 2 — Check and repair the Windows component store

DISM /Online /Cleanup-Image /CheckHealth

Quickly checks whether Windows has already recorded component-store corruption.

DISM /Online /Cleanup-Image /ScanHealth

Runs a deeper scan. This can take several minutes.

DISM /Online /Cleanup-Image /RestoreHealth

Scans for corruption and repairs the Windows image. It may appear stuck at one percentage for a while; do not close it just because the percentage pauses.

Step 3 — Repair protected Windows system files

sfc /scannow

Checks protected system files and replaces damaged copies where possible.

Step 4 — Restart and test

  1. Restart Windows after DISM and SFC finish.
  2. Test the original problem again.
  3. If SFC says it found corrupt files but could not repair some of them, run DISM RestoreHealth again, restart, then run sfc /scannow once more.
What if DISM fails?

Check the error code first. Common causes include no internet access, damaged Windows Update components, a heavily corrupted Windows installation, or a repair source that cannot be found. If Windows still boots, an in-place repair install may be a better next step than repeating commands indefinitely.

03

Startup

Computer won't boot or keeps restarting

First work out whether the machine has a power problem, a display problem, or a Windows boot problem.

If there is no power

  • Check the wall outlet, power board and charger or desktop power cable.
  • Disconnect docks, USB devices and external drives.
  • On a laptop, try the correct known-good charger if one is available.
  • Look for charge lights, fan movement or keyboard lights.

If it powers on but Windows will not load

  • Disconnect unnecessary USB devices.
  • Check whether the SSD or HDD appears in BIOS/UEFI.
  • If Windows Recovery opens, try Startup Repair.
  • Try Safe Mode if Windows reaches the recovery menu.
  • Recent driver or update problems may respond to System Restore or uninstalling the latest update.
Do not keep forcing restarts if the drive makes unusual noises, disappears from BIOS, or contains important data. A failing storage device can get worse with repeated attempts.
04

Display

Black screen or no display

A no-display fault can come from the monitor, cable, graphics output, RAM, GPU, motherboard, or Windows itself.

  1. Confirm the monitor or TV is on the correct input.
  2. Reseat or replace the HDMI/DisplayPort cable.
  3. On a desktop with a graphics card, make sure the display cable is connected to the graphics card rather than the motherboard unless the CPU supports integrated graphics.
  4. Disconnect extra monitors and docks.
  5. For a Windows display-driver reset, press Win + Ctrl + Shift + B. A beep or screen flash can indicate the driver reset was accepted.
  6. If there is still no BIOS/logo image, the fault is more likely hardware than Windows.
Desktop hardware checks

If you are comfortable working inside a desktop, turn it off, unplug it and discharge static before touching components. Reseating RAM can help after a move or upgrade. If the system has multiple RAM sticks, testing one known-good stick at a time can help isolate a memory fault.

05

Storage

HDD or SSD problems

Storage faults can cause slow startup, freezing, corrupted files, update failures, blue screens and computers that suddenly stop booting.

Warning signs

  • Mechanical clicking or repeated spin-up noises from an HDD.
  • File Explorer freezes when opening a drive.
  • The drive vanishes from Windows or BIOS.
  • SMART or health warnings.
  • Read/write errors, bad sectors or repeated file corruption.
  • Disk usage stays at 100% with very low transfer speed.

Basic checks

  1. Back up important data first.
  2. Check drive health with a SMART monitoring tool or the SSD manufacturer's utility.
  3. For a healthy drive with file-system concerns, an online Windows scan can be run:
chkdsk C: /scan

Scans the Windows file system without scheduling an offline repair.

!
Do not use repair scans as a first response to a physically failing drive.

If the drive is clicking, disconnecting or holding irreplaceable data, further reads and writes can reduce the chance of recovery. Clone or recover the data first.

06

Memory

RAM and memory faults

Bad RAM or too little RAM can cause slowness, random restarts, blue screens, corrupted installs, application crashes and boot failures.

Check normal RAM use

  1. Open Task Manager and select Performance → Memory.
  2. If normal work regularly uses most of the installed memory, an upgrade may help.
  3. 4 GB is very restrictive for current Windows use. 8 GB is a practical minimum for light use, while heavier multitasking often benefits from 16 GB or more.

Test for memory errors

mdsched.exe

Opens Windows Memory Diagnostic. Choose to restart and test. For intermittent faults, a longer dedicated memory test can be more useful.

Hardware tip: on desktop systems, test one stick at a time if the machine is unstable. A bad stick, bad slot, poor contact or unstable memory settings can produce similar symptoms.
07

Cooling

Overheating, loud fans or thermal shutdowns

Heat can make a computer slow down to protect itself, crash under load, or switch off without warning.

  • Make sure vents are not blocked by dust, bedding or a soft surface.
  • Listen for fans that grind, stop, or instantly run at maximum speed.
  • Check CPU and GPU temperatures with a trusted hardware monitor.
  • If temperatures climb quickly under light use, the cooling system may be clogged or poorly seated.
  • Older systems may need internal cleaning and fresh thermal compound if the original material has degraded.
  • Do not keep stress-testing a machine that is shutting down from heat.
08

Stability

Freezing, crashes and blue screens

Random crashes are often caused by drivers, RAM, storage, overheating, unstable hardware, damaged Windows files or software conflicts.

  1. Note the exact blue-screen stop code or take a photo.
  2. Check whether the fault happens during a specific task such as gaming, startup or copying files.
  3. Install stable Windows updates and device drivers from the PC or component manufacturer.
  4. Run DISM and SFC using the guide above.
  5. Test RAM and storage health.
  6. Check CPU/GPU temperatures.
  7. Remove recent overclocks, undervolts or unstable XMP/EXPO settings while diagnosing.
Where Windows records crashes

Reliability Monitor gives a simple timeline of application and Windows failures. Search Start for “Reliability History”. Event Viewer can provide more detail, but individual errors should be read in context because normal systems log many harmless warnings.

09

Storage space

Windows is running out of disk space

Very low free space can slow Windows, stop updates, break temporary files and cause applications to fail.

  1. Open Settings → System → Storage and review what is using the drive.
  2. Empty the Recycle Bin after checking its contents.
  3. Use Windows Temporary Files or Disk Cleanup rather than deleting unknown folders by hand.
  4. Move large personal files to another drive only after confirming there is a backup.
  5. Uninstall applications you no longer use through Settings.
  6. Do not manually delete Windows, Program Files, recovery or hidden system folders to make space.
10

Windows Update

Windows Update is failing

Update failures can come from low storage, damaged system files, broken update components, drivers or a pending restart.

  1. Restart the computer.
  2. Make sure the date, time and internet connection are correct.
  3. Confirm there is enough free space on the Windows drive.
  4. Run the built-in Windows Update troubleshooter if available on your version.
  5. Run DISM /Online /Cleanup-Image /RestoreHealth, then sfc /scannow.
  6. Retry Windows Update.
  7. If the same update fails, record the KB number and error code before making deeper changes.
11

Network

Internet or Wi-Fi is not working

First determine whether the fault affects one computer or every device on the network.

If every device is offline

  • Check the modem/router power and service lights.
  • Restart the modem/router once.
  • Check your internet provider for an outage.

If only one computer is affected

  • Forget and reconnect to the Wi-Fi network.
  • Disable and re-enable the network adapter.
  • Restart Windows.
  • Try Ethernet if available to separate Wi-Fi from internet faults.
ipconfig /flushdns

Clears the local DNS resolver cache. This can help when a site or hostname is resolving incorrectly.

netsh winsock reset

Resets the Windows Winsock catalogue. Restart the computer afterwards. Use this after simpler network checks, not as the first step for every connection issue.

12

Peripherals

USB device is not detected or keeps disconnecting

The device, cable, USB port, power demand, driver or Windows installation can all be involved.

  1. Try another USB port, preferably directly on the computer rather than through a hub.
  2. Try another known-good cable if the device uses a removable cable.
  3. Test the device on another computer where possible.
  4. Disconnect other high-power USB devices.
  5. Open Device Manager and look for warning symbols or a device that repeatedly appears and disappears.
  6. Install chipset/USB drivers from the computer or motherboard manufacturer when relevant.
13

Audio

No sound or Windows uses the wrong audio device

Windows can switch outputs after HDMI devices, Bluetooth devices, docks or driver updates are connected.

  1. Click the speaker icon and confirm the correct output device is selected.
  2. Check the application's own audio output setting if it has one.
  3. Disconnect unused Bluetooth or HDMI audio devices.
  4. Open Settings → System → Sound and test the selected device.
  5. Restart the Windows Audio service or the computer if sound vanished after a driver change.
  6. Check Device Manager for audio-driver warnings.
14

Laptop power

Laptop battery will not charge or drains quickly

A worn battery, incorrect charger, damaged charging port, USB-C power negotiation issue, background load or board fault can cause charging problems.

  • Use a charger with the correct voltage and enough wattage for the laptop.
  • Inspect the cable and connector for heat, looseness or damage.
  • For USB-C laptops, not every USB-C charger or port supports the required Power Delivery profile.
  • Check battery health before replacing parts.
powercfg /batteryreport

Creates a Windows battery report, normally saved to the path shown in the terminal. Compare the design capacity with the current full-charge capacity.

!
Stop using a swollen battery.

If the trackpad, keyboard or case is lifting, or the battery looks swollen, shut the laptop down and arrange safe battery replacement.

15

Security

Malware, pop-ups or unwanted software

Unexpected browser redirects, fake security alerts, unknown startup apps and heavy background use can point to unwanted software.

  1. Do not call phone numbers shown in browser pop-ups.
  2. Close the browser. If it will not close, use Task Manager.
  3. Check installed applications for programs you do not recognise.
  4. Check browser extensions.
  5. Run Windows Security / Microsoft Defender scans and install current security updates.
  6. Change important passwords from a known-clean device if you entered them into a suspicious page.
  7. If financial or identity information may have been exposed, contact the relevant provider as well as cleaning the PC.
16

Protect your files

Back up data before repair, reinstall or drive replacement

A repair should not begin with the assumption that the existing drive will remain readable.

  • Copy important documents, photos, desktop files and other irreplaceable data to a separate device.
  • Confirm the backup opens before deleting or reinstalling anything.
  • Check browser bookmarks, password-manager access and application licence details if they matter to you.
  • For cloud-synced files, confirm they have finished uploading rather than assuming an icon means the full file is stored online.
  • If the drive is failing, prioritise the most important data rather than trying to copy everything repeatedly.

When basic troubleshooting is not enough

Signs the computer needs hands-on diagnosis

Software repair cannot fix every fault. These symptoms often need hardware testing, parts, board work or controlled data recovery.

01

Drive is failing

Clicking, disappearing, SMART warnings, unreadable files or severe I/O errors need storage diagnosis before more repair attempts.

02

No power or no POST

No signs of life, repeated power cycling, diagnostic LEDs or no BIOS display can indicate RAM, power, motherboard or other hardware faults.

03

Liquid or physical damage

Corrosion, broken ports, impact damage and burnt components should be inspected before power is repeatedly applied.

04

Windows remains corrupt

If DISM, SFC and normal recovery options fail, a repair install, clean installation or storage replacement may be the better path.

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