Computer shuts off during POST

Hello all.

My problem started out last week while I was sitting and reading a book and I heard my computer suddenly shut off after running for two years solid without problems. When I tried turning it back on, it made it through bios and through loading windows and I was able to open Firefox, then it died again. On the second attempt, it died during bios. The first thing I thought was that it was a faulty power supply, even though mine was only two and a half years old and it was a 450w antec with dual rails.

Last night my new power supply arrived (650w antec with 3 rails) and I replaced the old one, connected everything, and my computer crashed while booting windows. The second time it died during bios. I tried resetting my CMOS and it still would not make it past bios.

my hardware is as follows;
Antec True Power Trio TP3-650 ATX12V 650W
2x Western Digital Raptor WD1500ADFD 150GB 10,000 RPM Serial ATA150 Hard Drive
ARCTIC COOLING Freezer 7 Pro 92mm CPU Cooler
pqi TURBO 1GB (2 x 512MB) 240-Pin DDR2 SDRAM DDR2 667
ABIT NI8-SLI GR LGA 775
Albatron PC6800GT GeForce 6800GT
Intel Pentium 4 530J Prescott 3.0GHz LGA 775 Single-Core Processor


Any suggestions would be greatly appreciated!!

 

So is it even making it past the post or is it just shutting down when it starts to run the post?

Also is it completely shutting down or is it rebooting?

 

It's currently making it past the post and beginning to boot windows before it dies. It's not restarting, it just shuts down completely.

 

In my original post I stated that my power supply was the first thing I tried. I just rebuilt my machine with a brand new 650W antec and it's still having this problem.

 

It's all good. I don't believe it's a problem with the hard drives, or the install, the install isn't more than a month old as my old hard drive died recently. ATM, the only thing I have connected are the drives.
Before I installed the new psu, I got it to boot up windows and was able to run it for about a minute until it died, so I'm pretty sure the boot sector is still ok. Were my computer able to make it long enough to get past loading windows, I think it would boot fine.

 

I'll try the boot to cd when I get home. One thing that I was thinking is that somehow my heatsink might have come loose. It is pretty heavy. But if that is the problem, I don't understand why my computer would just shut off randomly after working fine for a solid couple of months. It doesn't seem to me like a heatsink would just come loose while sitting idle.

 

If your heatsink has a fan on it make sure it's working too.

Tim, do you think the thermal paste might be all dried up? It kinda sounds like the cpu could be overheating.

 

I think that very well may be the problem. And the case I have, Antec P182, doesn't have a speaker for whatever reason so I wouldn't hear the warning noises. I'm going to remove my heatsink today and clean off the old thermal paste and reapply to see if that solves the problem. Thanks guys! I'll let you know how it turns out!