My late 2007 24" iMac has started doing spontaneous reboots (sometimes it freezes instead of rebooting, and I have to do a hard reset with the power button and sometimes a very loud crackling sound comes out the speakers as soon as it freezes and the sound continues until I do a hard reset). It seems to only happen while watching streaming video of any kind. At this point I'm still not sure if this is software related, or hardware related. I'm wondering if my video card or power supply has a problem. My hard drive died after 3 years and when I checked I found it was running consistently at 59 C degrees, which is only one degree below the manufacturer's max temp spec. I replaced the drive and have been using SMC fan control ever since, but I wonder if damage to other components was done in that first three years of baking. Around the same time, my Netflix playback became very choppy and is still that way. In addition to that, I have had to reinstall Silverlight three times recently, because Netflix video refused to play and I got a message saying there was a problem with Silverlight and it needed to be reinstalled. So that makes me wonder if the rebooting/freezing issue might somehow be software related. Before signing off I'd like to give a brief rant on how disheartening it is to find that Apple's heat management is so bad on this model. Without SMC fan control, my power supply sometimes hits 80 C degrees. I think it must be intentional, as a way of getting people to pay to have their computers either serviced or replaced after just 3 or 4 years. The OS should run the fans fast enough so these temps are never seen in the unit. This was the top of the line model when new, and not exactly cheap. It should last far longer than this. My G4 Powermac was still going strong at the 10 year mark when I sold it, and that thing saw MUCH heavier use than this iMac. I'd be interested in hearing from anyone who has had similar symptoms.