I do not know if this has been posted before or not... But I found [as have others] that it is a GOOD idea to exclude all of the Parallels .HDD files from a Time Machine Backup. Why? Parallels stores the entire Windows "hard drive" as a single file under OSX, and while this is transparent to the end-user, any time any "windows" file is updated [ie. everytime you do something under Windows], that ENTIRE file is marked as updated. My Time Machine backup had 250 gig of data on it in the first 8 hours... I removed the Parallels files from the backup sequence, and it dropped to 110 gig [and is growing very slowly]... more what I'd expect. There is an entire thread about this on the Parallels website as well.