I have a two-year-old iMac (operating system OS X 10.4) that has given me no end of trouble since I've had it. (Unfortunately I do NOT have the extended warranty.) The hard drive crashed for good about half a year ago, and I had it replaced by Apple. However, over the past two months or so, it "crashes" every few days. I get the flashing empty file icon, and even though it takes me a good 20 minutes of forced reboots, safeboots, unplugging, holding in the power button, waiting overnight, etc. etc. it does still restart eventually. Common triggers of the crashing: switching users, updating software, waking up from the screensaver or sleep mode (*especially* with a password lock). I have noticed a sort of low "wheezing" noise whenever it does crash. It also runs extremely slow as a general rule and has to "think" (spinning pinwheel) every few minutes. I took it in to the Apple store, but the only thing they could suggest was to reinstall the operating software. Yet when I try to start up from the original cds, it doesn't acknowledge the cd. Any help would be greatly appreciated!!!!