AFAIK, the way time machine is supposed to work is that when the drive fills up, it deletes the oldest copy to make room for the new one, right? But for some reason, for months now, it's been giving me the message that the drive is full and Time Machine cannot perform a backup. Any idea how to make it get past this? Do I just need to go in manually and delete things, or will that mess up its system of only backing up what's changed since previous backups? If it makes a difference, I have backed up multiple computers to this drive; I have a static backup of an old laptop, but my desktop is the only computer actively using Time Machine on it. It's a several-year-old Mac Mini running 10.6.8.