Paul is looking for software to allow him to backup each version of what he's working on. Leo says that's called "versioning." Windows 7 has versioning, called "Shadow Copy." He can enable it in his settings, inside System Properties Control Panel. He should look for a System Protection Tab, and enable Shadow Copy. It'll copy to a portion to the local hard drive that he can then backup.
There are several third party programs that can also accomplish this:
This is $55, but has a free trial.