You make want to check if the IDE cable is not shorted out. I had one shorted
out on me after I installed a second hard drive. After I replaced the IDE cable
it ran fine. All so it may be the CPU or bad ram. If it is the HD that is
failing. You can save you data to the new HD or back up every thing. Do not toss
out the bad HD in the trash before wiping it out.
http://abaababa.ouvaton.org/wipe/wipe.1.html
Some one can go. Oh what can be on this at the city dump. Most places recycle
before it goes to the land fill and it can be bad news.