I'm planning to use Time Machine after my next external HD purchase. I'm also planning to install Vista in boot camp so I was just wondering if Time Machine will back up both of these partitions, or only files on the Mac partition?
No it'll back up both, but it will only back up the stuff on the Vista partition in the mac side, which will not be recognized by the Vista side should you ever need to restore your HD. If you want to back up the files on the Vista side and have Vista recognize it, partition your external and use one of the partitions to back up from Vista.