Imac OSX 10.5, started getting allot of the pinwheel.. know next to nothing about this IMac, just use it for photo's/artwork/Safari/Gmail/CL. Googled problem, found Disk Utility..Do I need to insert start up disks to do that? Did it without 'em and Mac goes to Blk. screen before it finishes (both on verify/repair) It shows a bunch of errors!?!. I got OnyX and it starts out saying "volume error" and that I better back up.. How do I do that? (get a 500gig ex. HD?) IMac runs pretty fast other than typing/surfing. I'm a lost and clueless noob.. Thanks!