Trying to salvage my son's Power G4 Graphics ... problem started with grinding sound then no video. Won't shut down with reboot button ... unplug and restart, fans run, dvd drive runs but no startup sound and no access to hard drive. Suspecting a hard drive failure I have replaced with an identical new drive (hard to find) and still no response to reboot button, video, and new hard drive. Tried rebooting with original install cd to no avail. Any ideas or should I toss it. Thanks for any response.