I just installed Leopard and have a question about Time Machine: Is it safe to use an external hard drive which already has data on it as the Time Machine backup drive? That is, will Time Machine erase the existing data on this drive? The drive I have is a single partition. Sorry if this is elementary, but I haven't been able to find a simple, hit-you-over-the-head-with-it answer, and I want to be 100 percent safe before I proceed with this. Thanks!