Your PC is playing up and you want it sorted. No preamble needed. This Windows troubleshooting workflow runs from the fastest five-minute checks all the way through to DISM SFC repair, clean boot isolation and stop code diagnostics. Work through it in order and you'll find the fault.

What Actually Causes Windows Crashes and Slowdowns?

Before you start clicking things at random, it helps to know what you're actually dealing with. The Windows troubleshooting workflow is built around the real root causes, not guesswork.

Drivers are responsible for more Windows instability than almost anything else. A faulty GPU driver, a dodgy chipset update or an unsigned third-party driver can cause blue screens that look completely unrelated to the driver itself. The stop code will say something like SYSTEM_THREAD_EXCEPTION_NOT_HANDLED or IRQL_NOT_LESS_OR_EQUAL, and without digging into the minidump you'd never guess it was a driver at fault.

Corrupted system files are another big one. Windows Update can fail mid-install, a power cut can interrupt a file write, or a misbehaving app can overwrite a protected DLL. When that happens, Windows starts behaving oddly in ways that don't follow any obvious pattern. Random freezes, apps that won't open, settings that reset themselves. DISM and SFC exist specifically to fix this, and they work well when you run them in the right order.

Hardware problems are sneaky. A drive that's starting to fail will cause intermittent slowdowns long before it throws a SMART error. Bad RAM causes crashes that look like software bugs. Overheating causes throttling that makes everything feel sluggish, especially under load. And a failing PSU can cause the most baffling, unrepeatable symptoms you'll ever see.

Then there's the software side: background processes gone rogue, startup items from apps you installed six months ago and forgot about, and those 'PC optimiser' tools that actually make things worse by disabling services Windows needs. Third-party security tools are a common culprit too, especially ones that hook deep into the kernel.

So the workflow below is ordered deliberately. Quick hardware and software checks first, then system file repair, then isolation of third-party conflicts, then the nuclear options. Don't skip ahead.

Quick routeStart here

Windows Troubleshooting Workflow: Quick Fixes (5 to 10 Minutes)

Start here. Seriously. Half the problems I see on remote support sessions are fixed at this stage.

Clean Reboot and Task Manager Check Easy

Do a proper restart
Don't just close the lid or hit sleep. Go to Start, Power, Restart. A full restart flushes RAM, clears driver state and ends any hung processes. Hibernate and fast startup don't do this properly, which is why 'have you tried turning it off and on again' actually works.
Open Task Manager immediately after boot
Press Ctrl+Shift+Esc. Click 'More details' if you see the compact view. Sort by CPU, then by Memory, then by Disk. Look for anything sitting above 80% sustained usage. Common offenders: SearchIndexer.exe hammering disk after an update, MsMpEng.exe (Windows Defender) running a scan, or a browser with too many tabs open. If you spot something obvious, close it or uninstall the app.
Check free disk space
Open File Explorer, right-click your C: drive and check properties. Windows needs at least 10 to 15 GB free to operate properly. Below that, performance tanks and updates fail. If you're tight on space, run Disk Cleanup as administrator and tick 'Clean up system files' to remove old Windows Update files.

If CPU, memory and disk all settle below 50% after a clean reboot and there's plenty of free space, the problem may have been transient. Monitor for recurrence before going further.

Windows Update and Built-in Troubleshooters Easy

Check for pending updates
Go to Settings, Windows Update, and click 'Check for updates'. Install everything listed, including optional driver updates. A lot of known stability bugs are fixed only in recent cumulative updates, and running an old build is asking for trouble. Reboot after installing.
Run the relevant troubleshooter
Go to Settings, System, Troubleshoot, Other troubleshooters. If you're having performance issues, run the Performance troubleshooter. For audio, network or printer problems, pick the matching one. These aren't magic, but they do catch common misconfigurations and they log what they find, which is useful later.

Windows Update sometimes needs a second reboot before changes fully apply, especially after a large cumulative update. If things still feel off after the first restart, reboot again before moving on.

Intermediate routeKeep going if needed

Intermediate Windows Troubleshooting Workflow Steps (15 to 30 Minutes)

Still not fixed? Good, now we get into the proper diagnostic work. This is where most problems get caught.

Reliability Monitor and Event Viewer Medium

Open Reliability Monitor
Type reliability in the Start menu and open 'View reliability history'. You'll see a timeline with red X marks for critical failures and orange exclamation marks for warnings. Find the date your problems started and click on the events listed below the graph. This tells you exactly what crashed and when, often pointing straight to a specific app or driver.
Check Event Viewer for repeated errors
Press Win+X and open Event Viewer. Expand Windows Logs and check both System and Application. Filter for Error and Critical events (right-click the log, Filter Current Log, tick Error and Critical). Look for events that repeat around the time of your symptoms. Note the Event ID and Source column. For example, Event ID 41 from Kernel-Power means an unexpected shutdown, usually a crash or power loss. Event ID 7034 means a service crashed unexpectedly.
Cross-reference stop codes
If you're getting blue screens, the stop code appears in Event Viewer under the BugCheck event. Microsoft's Windows Error Reporting documentation maps stop codes to likely causes. MEMORY_MANAGEMENT points to RAM. NTFS_FILE_SYSTEM points to storage. PAGE_FAULT_IN_NONPAGED_AREA often means a driver.

If you find a specific app or driver named repeatedly in Reliability Monitor or Event Viewer, uninstall or update it before running any further diagnostics. That's your culprit.

Disable Recent Apps and Startup Items Easy

Uninstall recently added software
Go to Settings, Apps, Installed apps and sort by Install date. If problems started after installing something specific, uninstall it and reboot. This is especially relevant for 'PC optimiser' tools, VPN clients and third-party antivirus products that hook deep into the system.
Disable non-essential startup items
Open Task Manager, go to the Startup apps tab. Right-click anything that isn't from Microsoft or a core app you actually need and select Disable. Reboot and see if performance improves. You're not uninstalling anything here, just stopping it from loading at boot.
Check power settings
Go to Settings, System, Power and sleep, and make sure you're on Balanced or High Performance, not a custom plan from a tuning tool. Some eco or gaming modes set aggressive CPU throttling that causes intermittent slowdowns under load.

If you're dealing with a PC that's been running slowly for a while and you're not sure where to start, our slow PC fix guide covers the full diagnostic process including disk health checks and memory testing in more detail.

Advanced routeChange one thing at a time

Advanced Windows Troubleshooting Workflow Fixes (30+ Minutes)

Back up your important files before running any of the steps below. DISM and SFC are safe, but the clean boot and repair install steps change system configuration. Better safe than sorry.

DISM and SFC System File Repair Medium

Open an elevated Command Prompt
Press Win+X and select 'Terminal (Admin)' or 'Command Prompt (Admin)'. You need administrator rights or these commands won't work.
Run DISM in sequence
Type each command and wait for it to complete before running the next:
DISM /Online /Cleanup-Image /CheckHealth
DISM /Online /Cleanup-Image /ScanHealth
DISM /Online /Cleanup-Image /RestoreHealth
The RestoreHealth step downloads replacement files from Windows Update, so you need an internet connection. It can take 10 to 20 minutes. Don't close the window.
Run SFC after DISM completes
Type sfc /scannow and press Enter. SFC scans protected system files and replaces corrupted ones using the component store that DISM just repaired. If it reports 'Windows Resource Protection found corrupt files but was unable to fix some of them', reboot and run sfc /scannow again. This one often needs a second run before it sticks.
Verify the result
After rebooting, check the CBS.log file at C:\Windows\Logs\CBS\CBS.log for any remaining errors. The Microsoft SFC support page explains how to read the log output.

If SFC reports 'Windows Resource Protection did not find any integrity violations' after the second run, your system files are clean. Reboot and test.

Clean Boot to Isolate Third-Party Conflicts Medium

Open System Configuration
Press Win+R, type msconfig and press Enter. Go to the Services tab. Tick 'Hide all Microsoft services' at the bottom, then click 'Disable All'. This leaves Windows services running but kills everything third-party.
Disable startup items
Go to the Startup tab in msconfig and click 'Open Task Manager'. In the Startup apps tab, right-click each enabled item and select Disable. Go back to msconfig and click OK.
Reboot and test
If the problem disappears in clean boot, a third-party service or startup item is causing it. Re-enable services in groups of five, rebooting after each group, until the problem returns. The last group you enabled contains the culprit. Narrow it down from there.
Re-enable everything when done
Don't leave the PC in clean boot permanently. Go back to msconfig, re-enable the services and startup items you want, and reboot normally.

The clean boot method is described in detail in the HowToGeek guide on diagnosing Windows crashes, which is a good reference if you want more background on reading crash dumps alongside the isolation process.

System Restore or In-Place Repair Install Hard

Try System Restore first
Open Control Panel, Recovery, Open System Restore. Choose a restore point from before the problems started. This rolls back system files, registry settings and drivers to that point without touching your personal files. It's reversible if something goes wrong.
In-place repair install as the last software step
If no restore point exists or restore doesn't help, download the Windows 11 ISO from Microsoft, mount it in File Explorer, and run setup.exe. Choose 'Keep personal files and apps'. This reinstalls Windows over itself, replacing all OS files while leaving your data and installed applications intact. It's not a reset, it's a repair. Most deep OS corruption is fixed this way.
Full reset only as a last resort
If the in-place install doesn't fix it, go to Settings, System, Recovery, Reset this PC. Choose 'Keep my files' if you want to preserve personal data. At this point you're looking at a hardware problem or something very unusual in the software stack.

The in-place repair install requires a working internet connection or a matching Windows ISO. Make sure the ISO version matches your current Windows edition (Home or Pro) and build number.

For blue screen troubleshooting specifically, including how to read minidump files and identify the exact driver causing a stop code, see our blue screen troubleshooting guide. And if you suspect a misbehaving application rather than a system file problem, our Windows performance fix guide covers process isolation in more depth.

Preventing Windows Troubleshooting Workflow Problems

Most of the problems this workflow fixes are preventable. Here's what actually matters, in order of importance.

Keep Windows and drivers updated. Not just Windows Update, but firmware too. Check your motherboard or laptop manufacturer's support page for BIOS and firmware updates every few months. WHQL-certified drivers from the OEM are almost always more stable than the latest version from the GPU manufacturer's website, especially for business machines.

Avoid registry cleaners and 'PC optimiser' tools. Full stop. They cause more problems than they solve. Windows manages its own registry perfectly well, and these tools routinely delete keys that Windows or installed apps actually need. The resulting symptoms look exactly like OS corruption, because they are.

Maintain disk space. Keep at least 15 GB free on your system drive at all times. Windows needs working space for updates, virtual memory and temporary files. A full drive causes update failures, which causes the corrupted system files that then need DISM and SFC to fix. It's a chain reaction.

Create restore points before making changes. Before installing a new driver, a major application or a system tweak, open System Restore and create a manual restore point. It takes 30 seconds and saves hours of work if something goes wrong.

Monitor hardware health periodically. Use CrystalDiskInfo for drive health (it reads SMART data and flags early warning signs) and MemTest86 for RAM if you're seeing random crashes that don't point to any specific software cause. Catching a failing drive early means you can replace it before it takes your data with it.

Windows Troubleshooting Workflow: Summary

The Windows troubleshooting workflow works because it's ordered. Quick reboot and Task Manager check first. Windows Update and troubleshooters next. Then Reliability Monitor and Event Viewer to find specific errors. DISM SFC repair for corrupted system files. Clean boot for third-party conflicts. System Restore or in-place repair install if nothing else works. Each step either fixes the problem or gives you better information for the next one. That's how you fix Windows properly, not by reinstalling from scratch every time something goes wrong.

Windows Troubleshooting Workflow: Fix Any PC Problem