So with the iphone coming and requiring 10.5 + i needed to up from my ancient tiger to leopard. I thought i'd get my parents mac mini too while i'm in the upgrade mode. I did the mac mini first so i could "test" on them in case of bad things....sure enough. errors, issues, and it said it must reformat. the cool thing was that my parents didn't really store anything on there so i went ahead with that. Now though I need to do the iMac G5 (mine), I'd really rather not have to reformat etc. but will if need be. i've copied my hd to an external and have a copy of everything (so i think). What else do i need to do in case or before I upgrade the OS?