"iTunes could not restore the iPhone because the backup was corrupt or not compatible with the iPhone being restored." message after backing up, updating to new IOS 8, and trying to restore

I plugged my iPhone 4S in to my PC, opened iTunes, synced what's on my iPhone, backed it up, made sure it was backed up, and then clicked to update my iPhone. It was successfully updated but when I went to restore all my pictures, contacts, apps, notes, etc, the message "iTunes could not restore the iPhone because the backup was corrupt or not compatible with the iPhone being restored." It's currently at factory settings (The "Hello" screen) and when I tap "Restore from iTunes"(not iCloud), the same message pops up. I absolutely can NOT lose all the stuff on my phone. Please, if this has happened to anyone and found a way to solve it, please help. How do I restore my iPhone?