I got a 20 inch imac around august or september of 2007. I noticed after about 8-9 months it would randomly restart itself. I wasn't on the computer much then so I really didn't care. I then got a laptop in 2009 and didn't use the iMac very much. It continues to restart itself though. I read online that this was a known problem with this iMac and that it was a flaw in some of the hardware. I got Apple to replace something inside (I forget what it was now but I believe a circuit or something else along those lines) they even replaced it for free last year (years after I bought it) because it was a known problem. This didn't work. It continues to restart itself randomly. I am not sure if there is some screen shots I can post or what but if someone could help me out I would appreciate it, thanks.