Homebuilt PC restarting/won't restart

[CustosObscurus]

Recently I ordered some parts for a new PC. Being new at actually putting the thing together, I had a tech buddy of mine build it.

I've had 2 problems with it since I got it: restarting without warning, then, upon restart, saying 'A serious error has occured'; and tonight it froze, I did a hard restart, and it wouldn't power up.

Here are the system specs:

Windows XP sevice pack 2
Intel Celeron D 340 2.93Ghz
Speeze P4 Copper Cooling Fan Up to 3.4GHz
MSI P4MAM2-V Motherboard
Kingston 1024MB RAM
Ultra X-Connect 500W ATX PS w/2 80mm UV Fans
XFX GeForce FX 5500  Video Card
Creative Labs Sound Blaster Audigy LS 5.1
Seagate 250GB EIDE HD 7200/8MB/ATA-100 Hard Drive
2x NEC ND-3540A 16X DVD+/-RW DL Drive
Powmax Blue Acrylic ATX Case with 3 Blue LED Fans
Ultra Dual UV 80mm Round Cold Cathode Light Kit

The first time it restarted, I was in the middle of playing Diablo II. I don't remember what I was doing the second time. Tonight, it froze while I was listening to some music on WMP10. And now it won't restart.

If you have any clue what could be wrong, I'd appreciate it. I'd rather not have to test it part by part on another PC.

EDIT: I forgot to mention my LinkSys Wireless card.

Also, about 30 minutes after the computer wouldn't restart, it's working now. However, I'd still like to know if there's anything I can do to keep that from happening again.

[Dell4700]

Your system is likely heating to the point that it is either overheating the Mobo/components or any of your add-ons.

It means your cooling system is insufficient for what you are running, or you have a component that has become overly sensitive to your normal operating temperature.

If your system has run in this configuration for some time without problems, I'd suspect any new component first, then I'd check existing stuff for abnormalities.  Your power supply may be insufficient or going bad.  Your graphics card also may be failing.

Try running the system bare bones (drive, PS, graphics) then add other stuff until you see the problem again.  Give it enough time to heat to operating temps.

Dell

[CustosObscurus]

Well, the power supply is 500 watts, which I would think is sufficient. Also, the case has 3 fans running plus the power supply fan (two in and two out), so I don't think that it's overheating. But I'd like to get this taken care of, so can you recommend an easy way to test the temp?

All the parts are brand-new; I bought them about a month ago, which is when I put it together. Could the parts have failed this rapidly? Or do you think they could have been faulty in the first place?


EDIT: I downloaded PC Wizard 2005 and it said that after running for about 20 minutes the cpu is heating up to about 45-55 degrees celsius, with the motherboard and hard drive at 35 and 29 respectively. I haven't been running it very hard; just some internet browsing and music playing.