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. The error can come up on Windows 10 and it’s predecessors (Windows 7, Vista, 8 and 8.1). Methods described in this guide will work on all versions of Windows (stated above). Due to numerous causes of this error, i have not found a single fix that works; for many users a mix and match of fixes has worked which i have listed in this guide. It would be best to go with each method described below and test after each method until it is fixed.
Optimize and Defragment Your Drive
Hold the Windows Key and Press E. Choose This PC from the left pane if you are using Windows 10/8 or 8.1. If you are using Windows Vista / 7 then proceed to steps below.
Right-click your Disk Drive and choose Properties. Then click the Tools Tab and choose Optimize (Windows 8/8.1/10) and Defragment (Windows Vista/7) and run it.
After the disk has been defragemented; reboot your system and test.
NTFS Files To FAT32 Format
If you are copying files from a NTFS format to FAT32 Format, then run the hotfix below.
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
Then, in the right pane ; right click and choose NEW and select DWORD Value
In 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. If it still won’t work then process to Method 3.
Once the above has been modified, go to Command Prompt; and copy the data to hard disk using the copy commands.
Run Chkdsk to CHECK DISK for Errors
Instructions for doing a chkdsk can be found at: https://appuals.com/run-chkdsk-reboot/