How to Run a DISM Scan in Windows (It Actually Works)
If your Windows PC suddenly starts acting a bit wonky—like slowing down, update errors, or odd system files popping up—you might need to run a DISM scan. Honestly, I didn’t pay much attention to this tool at first, but after a few frustrating nights troubleshooting, I realised it’s actually pretty handy. It’s one of those hidden gems built into Windows that can repair your system image without the need to do a full reinstall. It took me a bit to get comfortable with it, especially since some options might be grayed out or missing depending on your setup, but once you understand how it works, you’ll find it a lifesaver.
What is DISM Anyway, and Why Should You Bother?
DISM stands for Deployment Image Servicing and Management—yeah, a bit of a mouthful. Think of it like a doctor for your Windows system image. It checks for issues, repairs corrupt files, and can even replace damaged bits inside the system image. If you’ve seen errors during updates or your PC feels flaky, faulty system files could be to blame. Instead of reinstalling Windows from scratch, running DISM can often fix things quickly and safely. Just be careful—messing with system images can be risky if you’re not sure what you’re doing, especially if you accidentally clear certain options, which could lead to data loss or disable features like BitLocker. So, follow the instructions closely and don’t run commands blindly.
How to Open Command Prompt or PowerShell with Administrator Rights
This part always trips me up—if you don’t run the command prompt or PowerShell as an administrator, your commands will just hang and give you that “Access Denied” message. To open the right window, press Windows key + X. A menu will pop up. Look for Windows Terminal (Admin) or Command Prompt (Admin), depending on what version of Windows you’re running. Sometimes, it might be called differently—for example, on older PCs, it might be PowerShell (Admin). If you see PowerShell (Admin), that’s just fine—you can run the DISM commands from there. Alternatively, search for ‘Windows Terminal’ in the Start menu, right-click, and select Run as administrator. The key is making sure it’s an elevated window—that’s where the magic happens.
The Basic DISM Checks
Once you’re in the terminal with admin rights, here’s where I usually get started. The first command I run is:
DISM /Online /Cleanup-Image /CheckHealthThis command doesn’t make any changes; it just checks if your system image appears okay or if there are problems. If the output says “The component store is repairable” or “No component store corruption detected,” that’s good news. But if issues are reported, that’s when you need to dig a bit deeper. I usually follow it up with a more thorough scan.
Diving Deeper with ScanHealth
Next, run:
DISM /Online /Cleanup-Image /ScanHealthThis one can take a while—anywhere from 5 to 20 minutes, depending on your hardware and how much corruption there is. I’ve noticed it sometimes seems to do nothing for a bit—that’s normal. It’s doing a thorough check of the image. If problems are found, it will flag them here, explaining what needs fixing.
Fix It with RestoreHealth
If ScanHealth reports issues, the next step is to run:
DISM /Online /Cleanup-Image /RestoreHealthThis is the repair command. It can take quite some time—sometimes over 20 minutes—especially if Windows needs to download recovery files from Windows Update. During this process, it might seem like nothing’s happening—don’t panic. Just let it run its course. Once finished, I recommend rebooting your PC and rerunning the scans. Sometimes, a second pass is needed if issues are stubborn or new problems show up during the repair.
Extra Tips and Troubleshooting
Running DISM isn’t always straightforward, especially on OEM machines or if Windows Update isn’t working properly. If the default source can’t fix your image, you can specify an alternative source manually. For example, you might run:
DISM /Online /Cleanup-Image /RestoreHealth /Source:wim:X:\sources\install.wim:1 /LimitAccessHere, ‘X:\sources\install.wim’ is pointing to a mounted Windows ISO or installation media. You’ll need to mount an ISO file first or copy the install.wim file to a location you can access. Sometimes, your system won’t download fixes from Windows Update and needs a helping hand. I encountered this on a work machine, and using an untouched ISO source fixed the issue.
After running these commands, I often follow up with sfc /scannow—which scans and repairs any remaining corrupted system files that DISM might have missed. Also, for a complete check, review the logs in C:\Windows\Logs\DISM\DISM.log. At first, those logs look intimidating, but they can offer clues if problems persist.
Heads up—DISM isn’t magic. It can fix many issues, but if your PC is really knackered or files are severely damaged, you might need more drastic steps like a repair install or a full clean installation of Windows. For most problems, though, these commands are surprisingly straightforward once you get the hang of them. Just be patient during scans and repairs—don’t rush the process. Also, if this is an older PC or you’ve recently updated your BIOS/UEFI, make sure it’s up to date, as firmware issues can cause subtle problems that DISM can’t fix.
Hope this helps — it took me ages to figure out how this all works. Hopefully, it saves someone else a bit of hassle and a wasted weekend.