I deleted my appdata\roaming\apple computer\mobilesync\backup files and now I can't backup
Did you delete the Backup folder too? If so, if you recreate the Backup folder, you should be able to back up again :)


Windows 8 and 10: In the Windows search bar type %appdata% (with the percents) and press return/enter. A file browser window will open to the Application Data folder. (or Roaming inside of Application Data)
Windows 7, Vista, XP: From the start menu, select Run. In the run box, type %appdata% (with the percents) and press return/enter. A file browser window will open to the Application Data folder. (or Roaming inside of Application Data)
From there, navigate to Apple Computer (creating if needed) > MobileSync (creating if needed), and then create the Backup folder again.


If that's not it, can you let us know what error you're seeing in iTunes, and what version of Windows you are on?