Well,

It ran good for a few days but now my computer freezes after about an hour of use. Every when the CPU is Idle.

It is an Athlon 2900 XP with a 450 watt power supply. When the power supply hisses slightly is when the problems start. They are video problems too. The screen gets discolored or broken white letters even at startup. The videocard worked in another machine preveously, but sometimes the monitor just goes to standby mode.

The CPU is running a little hot at 65C with a big load. And when I put a load on it with a game the computer has gotten progressively worse over the last few days. It use to be able to run a game for a little bit, but now it freezes the computer almost immediately. And now I cant even reinstall windows without the monitor going to standby for some reason.

Will changing the new cheap power supply to one that is Athlon ready, and not cheap do the trick? I have added a battery back up AC device that stablized the voltage from the house because the refrig use to drive my computer nuts.

Sounds like you better replace that power supply real quick anyway!
... and check under the hood for melting components

this could be caused by poor heat dissipation from the cpu, if the problem occurred after the hsf was taken off/put on. did you recently take the heatsink out of the socket for any reason? when was it installed? you should also look for bad capacitors on the motherboard.

Got a 500watt power supply by Compusa to see if the original power supply is the culprit. It is.

Now the machine is stable again with the new power supply. However I still have a Athlon 2900 XP running at 100% at 66C.

The old PS is weird because it sucked air out. This new one sucks air in. The new PS is also Athlon Approved.

I have a cubby cabinet in my desk for the Tower. Did putting the old PS in there mess it up?

Also I am thinking I can get more bang for my buck, and I will need it for this desk cabinet. Any recommendations on Power Supplies for under $60-70?