Invalid MS-DOS Function Error

Invalid MS-DOS Function comes up when you try to move, delete, copy or rename files. This is a file-system error which usually affects the file functionality only, but since it is very annoying it limits your usage. Methods described in this guide will work on Windows 7.

Edit System Policy via Registry

Hold the Windows key and Press R; then type regedit and click OK

Navigate to the following path in the registry editor

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\System

Then, in the right pane ; right click and choose NEW and select DWORD Value

Enter the value name field; type CopyFileBufferedSynchronousIo then press ENTER.

Right click the newly created value CopyFileBufferedSynchronousIo, and choose Modify

Type 1 in the value data box and hit enter/ok. Then reboot your PC and test to see if it works.

Now try copying files again and you will notice the problem is solved. I hope you  will find this method working.