First... going to clarify some instructions above then add some new information. 🙂
If you still have the device (with the files on it) to make a new backup, you should completely erase the existing backup (or rename the folder for it, which is good enough to "hide" it from iTunes) and then make a fresh backup.
On a Mac your backups are in /Users/<your username>/Library/Application Support/MobileSync/Backup
(Open Finder, hold the Option key, and select "Library" from the Go menu to get to your user's Library folder.)
On Windows, the fastest way to get to your backup folders is:
- (Windows 7 and below) Start -> Run -> type %appdata% (with the percents) and press return.
- (Windows 8) Search -> type %appdata% (with the percents) and press return.
- (All) From Application Data, navigate to Apple Computer, Inc. -> MobileSync -> Backup.
You can match your device identifier with the backup folder name by clicking on the Serial Number field in iTunes (which will switch it to your device identifier.)
If you no longer have the device to make a new backup, then you're in more of a pickle. I work for a company that does iPhone/iPad/iTouch forensics, and we've seen these corrupted backups a lot recently -- so we decided to make a tool to fix them. You can try out Decipher Backup Repair, to look at what the errors are in your device's backup in iTunes, and see how we can resolve the errors. I'd love any feedback, if you want to contact us (via our website linked here) and provide it (feel free to mention my name, Kelly, since I do most of the work on Decipher Backup Repair.)
I hope this information helps someone if they have a corrupted backup!
(Note: As I mentioned, I work for the company I've discussed above, so I stand to benefit, either financially or otherwise, from the links I'm recommending.)
