As an FYI if you have a large external drive formatted for the Mac you can use Disk Utility to create a compressed image of the entire drive. It's also free with the OS, and a disk image will put your machine back exactly the way it was at the time of backup.
This has some serious advantages in the event of a catastrophic problem, so I highly recommend everyone create one. Say your hard drive fails, you can replace it and be up in running very quickly, then use Time Machine to get the files you've changed since. No need to reinstall or configure the OS and software. It's about the fastest restore you can get.