You didn't reveal what you were trying to backup or the backup software. We know that the Microsoft backup software should be avoided so why not copy what you can't lose to that drive using Explorer?
Someone was nice enough to give me a brand new 250GB external drive. Since I just purchased a new PC with Windows 7 installed, I thought the new drive would be perfect for doing backups, (something I've never done before.) Windows 7 said I should partition the external drive to an NTFS format, and I figured out how to accomplish that. But - once I tried to do the backup I got a message something like this - "are you kidding... this drive is way too small buddy." So, now I think I'm gonna use it like a very large desk top thumb drive... My question is, should I try to un-do the NTSF format? I'm asking cuz I have absolutely no idea what an NTSF partition is.