I am looking at buying a new Hard drive and need to know how much space TM takes up. Currently I have about 150gb filled on my main drive all of which I plan to back up. How exactly does TM work? The reason I am asking is because I have found a nice HDD but there is a $75 difference in 1tb and 500gb. I also plan on dedicating about 150gb as a place to store my movie files. So would 350gb-formatting be enough space to back up my 150gb (well 100gb once I move the movie files) for a decent amount of time? (2-3 weeks?) Thanks for the feedback I've only been on leopard for about 4 months (from tiger) and don't know how TM works.