Invalid MS-DOS

Hello. I am having an issue. Whenever I try to delete or move an item, a message pops up and displays "Invalid MS-DOS Function" I can't seem to get past it so can someone help me? Thanks!

PS I'm new to this forum so.......


Windows Forum Admin
Staff member
Premium Supporter
I've seen this problem, and it's origin and resolution is kind of a puzzle. Many people have had this problem and there are multiple solutions which seem to have worked for them. Try these (reboot between each and try deleting your files)

1) Do a "chkdsk /f /r C:" at an administrative command prompt, allow it to run and finish (make take some time)
2) Defrag the hard drive using the Windows defrag tool
3) Run "sfc /scannow" at an administrative command prompt
4) Run "DISM /Online /Cleanup-image /Restorehealth" at an administrative command prompt

Would be interested in knowing which if any of these steps has resolved the issue for you.

If you mean reboot, doesn't that delete everything off your computer?


Microsoft MVP
Staff member
Premium Supporter
Microsoft MVP
No - that would be a re-install - reboot just means power off (log off, not just switch off) and back on again.

So, it just logs you off and logs you back on? Is that what you mean?

By the way, I have heard about the method of defragment and optimize drives. I optimized the storage (for mines, it's HP (C:)). And I've waited (yesterday) for like 5 hours. And I've wondered, how long is it suppose to take? Also, is it good to use this method? The steps for this method is.....

Step 1: Search for Defragment and Optimize Drives and then open it.

Step 2: Click on whatever storage drive you are using.

Step 3: Then click optimize

Step 4: Wait until this is finished then restart you computer.

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