I'm on a 24" early 2008 iMac with a 500GB hard drive. I'm thinking of getting an external drive of some sort to run Time Machine backups. I already make DVD-R DL disc backups about once a month, but I want to have something to backup my data inbetween those burns just in case. So far I'm looking at the Western Digital Passport 500GB USB 2.0 (previous model, not the new one with non-removable software partition). I figure it's big enough since I also use bootcamp (don't need this backed up) and my Mac OS X partition is 445GB with around 300GB available. There really isn't alot to be stored here, but I like having a drive bigger then what I need. I may store large files in the future. Would a Firewire 400 drive improve things quite a bit in my situation? FW800 enclosures are out of my price bracket (looking at OWC) and I could get a FW400\USB 2.0 enclosure and do it myself. I don't plan on using this drive except for Time Machine, and I'd like to set it up (if possible) to do backups at night when I'm not using the computer. I've heard the initial TM backup takes a long time. What would you suggest I do?