The Windows Backup 0x80070020 error is a sharing violation error, there is a file or files that have open handles to another process or processes that are locking the file or files from being copied by backup. someone I helped with this error had the issue with his C:\Users\<Username>\AppData\Roaming\Microsoft\Windows\Cookies\index.dat file. I had to use Process Monitor to find out which file was actually locked. The only way I managed to resolve it was to create a selective backup to exclude the C:\Users\<Username>\AppData\Roaming\Microsoft\Windows\Cookies folder with that persons permission. Just a note that it might not be that file that is locked, it could be any other file being backed up. The Process Monitor filters I used were: Command Line contains C:\windows\system32\svchost.exe -k SDRSVC Result is SHARING VIOLATION You can download Process Monitor fromhere.