iTunes cannot restore

So I backed up my dad's iPhone 5 and reinstalled iOS 8.2. Then it tried to restore from a previous itunes backup but it failed and said "iTunes could not backup the iPhone because the backup was corrupt or not compatible with the iPhone." I tried restarting the windows etc. The apps were installed but they didn't have the data, like whatsapp messages or app settings. So how do I fix this?

PS: That decipher repair guy, I tried your software but it didn't find any backups on my pc (there are backups and i can see them on itunes) so if you're going to advertise your software, don't, or make your software work.