Shuts Down While Booting Up XP

So I run the newest updates on XP Pro. I think my HD is dying. When Windows loads up, computer shuts itself off now matter how I try to get there. Safe Mode, etc etc.
Time for a new HD?
The PS was replaced last July.

Have you tried booting from a CD or external disk? That would either confirm or eliminate the HDD as the source. I'd guess some hardware problem other than the HDD; my first guess would have been the power supply but that seems less likely since it was just changed recently.

Yeah, I'm going there but this HD is 4 years old. I think it is that or the OS itself.
Keep them coming. I'll get back to everyone on the CD booty.

Well, at least hard drive storage is cheap these days. I just had to replace one: 500 GB, $80, and that was for a laptop drive. I've seen 2 TB USB external drives going for $120 or so.

Funny to think of being pleased the day when I was finally able to buy a 1 GB drive for less than $200. Man, a whole gigabyte--I thought I'd never fill that up!

I've seen this happen before. It may well be a bad or misconfigured video driver. And, naturally, since you can't get into XP (not even in Safe Mode) to reconfigure it, you're stuck.

Try booting from the XP CD and see if you can get into the Recovery mode.

It's also possible (though unlikely) that a sector or three in the boot area have gone flaky. See if you can get your hands on a copy of Spinrite to check the drive.

OK, could be the PS. Does not even get to the OS now before it cuts off. Going to take it apart now. Guess I'll regrease the thermal contact of the CPU while I'm in there.
The old PS that I took out initially was a 300watter. It was still working but I needed a fatter one to power the graphics card which required a minimum of 425. My last 500w PS lasted 3.5 years.
Oh goody. Maybe I'll get into breaking down the new PS.
Yippie for me.

And they're laughing at me now. They wanted to sell me an extended service warranty for $30 back when I bought it.

Trust me , the extended warranty is never worth it . Reseating the memory chips is always a good first step . I had very similar symptoms on my P4 Windows XP pro machine a few days ago , it wound up being a bad boot sector on the HD . Now , with a different drive installed as primary , the old drive works , for now . Before the swap , it'd stall at the screen that says "Windows is starting up ". I actually had to call Microsoft to get my reinstall authorized. It was not a complete ordeal , just a minor pain .

It cut off while I was in the bios.

Been working on reattaching one of the plastic tab that holds the heatsink down on top of an AM2 socket. The thermal grease was bone dry and there was no real contact between the CPU and the heatsink.
The CPU draws 125W so I think it heats up pretty quick. I'd be more comfortable if I could find a tiny screw to add to securing it.