I'm somewhat of a mac n00b and have a fairly basic question. I've used about 140gb of my MBP's hard drive, but have deleted about 20 more gigs of material, so am now with about 40gbs free. Now, I know with my old windows pcs, that once you used the hard drive room, even if you deleted gigs worth of data, you never went back to the performance you had prior to using up that hd space in the first place. does the same hold true for macs? so i ask you guys, when i upgrade to leopard (hopefully within the next month!), should i do a complete reformat first? or does freeing up hard drive room do the same trick on macs? any help would be appreciated. also, is it possible to backup applications?