my computer suddenly shuts down.

[joy83]

I have a Dell Dimension E521, I bought it 2 months ago and after that I pimped it with an extra gig of RAM, a new psu and a video card. Here are my specs as of now
AMD Athlon X2 3800+ Dual Core Processor
2 GB RAM (4 x 512MB) (added 1 GB but the same brand, one friend sold his ram to me) EVGA geforce 7900 GS KO 256 MB GDDR3 PCI-E video card (new addition)
500W Coolmax PSU (new addition)
160 GB Hard Drive
19" Proview Widescreen LCD monitor

Now the problem is sometimes (may be once every two days), the computer shuts down itself while I am working. Now its not a normal shutdown because the screen suddenly goes blank and I see no lights on the tower. I then have to switch it on again and then everything seems fine until the next time when it will happen (which I dont know when because there are no prewarnings). I dont know whats the problem, I have also checked the temperatures of different components, like right now the temp is (10 mins after the last abrupt shut down)

Hard Disk - 40 C
GPU - 50 C
CPU Core 1 - 24 C
CPU Core 2 - 26 C

I am usually surfing the net when it happens so I am not even stressing the CPU out to its limits. Does somebody have a solution? Thanks,

Update - I downloaded the Windows memory diagnostic tool and ran it before the boot, it seems like there are no errors with the ram. It passes all the tests.
So what is the conclusion now? Possible problem with PSU? Is there any diagnostic tool for the psu or any other way to check it?

Can there be a problem with the video card too? I bought it recently from newegg and it shouldnt have a problem. Its a

EVGA geforce 7900 GS KO 256 MB GDDR3 PCI-E video card. Please help
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[tommytran]

How about software configuration, do you have the latest antivirus software on your system? Have you tried to take a look at the event log to see if there is error?

 

[joy83]

I have the latest antivirus progam installed and I think all the softwares are working correctly. I haven't seen the event log.

I am wondering if I should revert back to my old PSU of 305W and see if the problem persists or not. What do u guys think?

 

[btcomm1]

I think that you should run memtest on your system.

 

[oynaz]

Pull out the extra RAM you have put in. If the problem goes away, you have found your culprit. If not, RMA the computer and let Dell fix it. (I suppose it is still under warranty).