my mac has a 160GB drive. my backup drive is 500GB. i've been using time machine for a while, and then i got an error message: Can't back up, the drive is too small for the backup. Sorry, asshole, buy a new hard drive. then i realize i accidentally deleted a file i need, and although the backups are on the drive, Time Machine doesn't see them. what the hell? isn't time machine supposed to delete the oldest backups and replace them with new stuff as you go forward? it can't be that you just have to keep buying more and more hard drives to keep this thing happy.