I have installed a different hard drive in my iMac and ran the system restore disk that came with it and it re-installed everything just like it came from the factory, but after about 5 minutes of running it locks up and then dosen't want to reboot. I have reset pram reset nvram replaced battery, don't know what else to do. Anyone have any ideas? Brad

This is a common problem I've seen on some revisions of the slot-loading iMac where the motherboard has been removed, damaging a thermal transfer pad which provides cooling to the processor. This can cook the processor itself. You didn't remove the motherboard at all, did you? Otherwise, did your iMac work fine with the last hard drive? Did you ensure that the new hard drive is set to Master (some companies preset their jumpers to Cable Select)? If you have a slot-loading iMac, you can try resetting the motherboard. Shut down the iMac and discconect the power cord. Disconnect the backup battery for a good fifteen minutes. Replace the backup battery. Press the reset button on the motherboard. Do *not* hold this button for more than a second. This can crash the PMU and kill your backup battery in a couple of days. James

This isn't a slot loading iMac, and the problem presented itself befor the motherboard was ever removed. I had been told it may be a bad hard drive that is why I changed it, but it still has the same problem as it did with the old hard drive. I have reset the motherboard and replaced the backup battery with a new one, nothing seems to work. I am wondering if it is a power supply, motherboard, or something els. Brad

It could be a problem with the processor perhaps or RAM. Try with only 1 piece of RAM at a time (if you have 2 pieces installed). Try reseating the processor (remove it out of it's slot, then press it in again snugly). Are you missing the heat sync on top of the processor? Is the main fan running okay? Overheating can cause problems once the computer warms up. Try running with no peripherals hooked up to it. Hopefully it's just the RAM, but it could be something more serious. James