Fail, fail, fail...Hardware issue

I'm not a hardware guy, so when it comes to computers just randomly shutting down I start to get nervous.

I checked the disk, made sure the windows system files are not corrupted, swapped memory and the problem still persists. I've narrowed it down to three things:

1. Bad PSU
2. Overheating CPU
3. Bad MOBO

Whenever I check the total CPU (AMD Dual Core) temperature immediately after a shutdown, it is usually around 40°C / 104°F. So I don't think it's overheating.

What happens is I'll be playing, browsing, or just starting my e-mail, or leaving the computer alone and it will just stop dead. You can hear all the fans spin down and then nothing. I can start the machine back up immediately, and sometimes it will work a while ( even a day ) or sometimes it's just 5 minutes before the next one. No blue screen of death, so I am pretty sure it's not a software issue.

My gut feeling is the power supply is going bad. Which would be ok since it's not that expensive. Am I headed in the right direction? Or is there something else I need to check?

TIA,
Keeper

It could also be a bad ram chip. I had this problem once and it did the same thing-shut down. Tryb removing all but one chip and switch them out until you find a bad one or you eliminate tha as the problem.

I have 2 1GB chips. I removed one and it happened, swapped it out for the other one and it happened. That's where I'm starting to think maybe bad mobo or maybe bad psu.

What does it say in the event log?

There's nothing there, no errors warnings or info. I can't find any dump files either. It just blacks out completely. I start it back up and it goes on like nothing happened. I'm about to JIHAD it TBH. My wife was about to start up on something for a side business and I was going to get more RAM. I might just do that and remove the current two sticks completely to see if that is the issue. If not, then I'll have 4GB total.

sounds like the power supply to me, or even possibly a surge protector going bad. Switch the power cord to a different outlet all together just to rule that out. If problem still persists I would go ahead and buy another power supply. I like to keep things like power supplies oh hand just for this reason, with PC's sometimes the only way to diagnose problems is by process of elimination.
You could buy some ultra cheap one, or just find some old pc at a garage sale, rip the PS out and try it, if thats it then buy a good one. BTW what kind of PS do you currently have in there?
Theres many things that could cause it tho, even a bad capacitor on the mobo. If you rule out the PS my next step would be to look on ebay for the exact same mobo, I have done this and found replacements for as low as 20.00. It is real easy to swap everything to a new like mobo and you dont have to reinstall windows or anything if you get the exact same one. Just check the bios versions on both and you may need to update the bios version at a minimum.

A while back i bought a PSU a good 1 themrmaltake 1000W it powerd up my PC but after a while it would swith PC off without warning, tried to restart but no power from PSU 20 mins go by still no power, turns out it was the thermal cut out causing it to shut down until cool enough to start up again.
Needless to say i sent the fecker back.

Actually I thought about replacing my PSU with Mr. Fusion ( no, not WT or KO ) and adding a flux capacitor for good measure

I think I'm gonna steal a PSU from work over the weekend and see what happens. If it works well I'll go get a new one. Been playing so much TF2 lately beginning to wonder if a spy is sappin my puter

EDIT: D'OH. I just upgraded my system last year and failed to realize that I forgot my PSU. Here I thought I might have a chance for a return. Turns out, my current PSU is more than enough for my system, so I'll just get the same wattage (500).

Did you make sure to clean it out?
A CPU problem such as over heating or damage can cause this as well as PSU

http://www.buy.com/retail/product.asp?sku=203270718 here is a good PSU for a decent price

On the other hand if you dont know what you can do is goto a local store like best buy and purchase a part then bring it home and try it, If it does not fix the problem you can just return it. Even if it does fix the problem you can return it and buy something you really want since they dont have jack for selection.

I've tried that before. Seems I remember most don't accept opened returns on electronics anymore. Maybe I could find a store, but I'll just rip one out of a computer here at work tomorrow and test it out this weekend. Too bad we don't have a shrink wrap machine

EDIT: On advice from a clanmate and L2k, I moved the power cord to a different source other than my UPS and the problem seems to have gone away. I'll evaluate it over the weekend, but if this is the case, then I'll keep the new PSU as a backup.