Ok, so, for some time, my computer shuts down and I'm unable to start it again until i unplug and plug it again. When it shuts' down the case light is still on like the PC is still on but everything inside is shut down. I've noticed that this happens mostly when I'm playing a game.
Here are my components:
CPU: Intel(R) Pentium(R) 4 CPU 2.40GHz
Motherboard: Intel Silver Reef D845PESVATI
Graphics: CardATI Radeon 9550 / X1050 Series
Memory: 2 Ram cards one of 1gb and one of 512mb
Hard disk: WDC WD1600JB-00REA0
Sound card: C-Media CMI8738/C3DX Audio Device PCI

I've read some other topics about this and found someone how had almost the same problem as me and he fixed it by buying a new PSU. But he had problems all the time, i mean his computer shut down no mater what, mine shuts down when paying a game.
My guess is that the problem is from either the PSU or the graphic card. But i have some concerns about the HDD as well.

Thank you, and looking forward for your advices.

My first guess would be heat. A computer will shut itself down at a certain temperature to protect itself from damage.

Can you get a hold of your CPU/Video card temperatures for us?

Yeah no problem, let me search and install a software to measure the temperature....

I've installed SmartFan and i don't see any thermometer for graphics card, i only have:
CPU: 39C
Internal Temp: 40C
Remote Temp: 39C
HD0: 33C
This is on IDLE...

And this is when i play the game
CPU: 45
Internal Temp: 41
Remote Temp: 40
HD0: 33C

Constantin Chirila said:
Judging from the temperature you provided it is not a heat issue.

What power supply are you using?

For video card temps you can use "ATI Tool" or "ATI TrayTool". I would think a card monitoring utility came with your video card, but here's the link to "ATI Tool"...the simpler utility.
http://www.majorgeeks.com/ATITool_d4109.html

Was wondering why you first thought it might be PSU and then don't tell us what PSU you have.

Have you calculated your total system power requirements and compared that to your PSU's specified maximum outputs? Have you done the same for each power rail? For example, even if your total wattage is lower than the total wattage supported by your PSU, the wattage required on the 12V rail might be higher than your PSU can supply on that particular rail. Check the PSU label and you'll see what I mean.

Are you over-clocking the CPU or RAM?

You might also want to test your RAM using MEMTEST or similar. You can get it individually or included in UBCD.

You get a thorough system test suite in UBCD (Ultimate Bood CD). The self-booting CD tests multiple system components: memory, CPU, hard drives, peripherals, etc. It does a very thorough job and is extremely easy to use.

Although it's reported version ver4.1.2 is available, the latest version I could obtain was 4.1.1
http://ubcd.sourceforge.net/
http://ubcd.sourceforge.net/download.html
You can download a .iso, .exe self-extracting, or .zip file depending on what connection speed you have. (download filesizes range from 87mb to 115mb) The .iso file is easiest as you just download it and then burn the .iso image to a CD using Nero, or CDburnerXP, or burnatonce, etc.

MD5/SHA-1 Hash Verification
I do recommend performing a hash verification to make sure your downloads aren't corrupted. Long downloads tend to be somewhat vulnerable. Use a program like freeware Fingerprint to calculate the MD5 hash and compare to the value provided by the download site.
http://www.majorgeeks.com/FingerPrint_d4388.html
http://www.2brightsparks.com/


edit-add atitool link

Ok, sorry for not responding for this long...

First of all my PSU is a 350W Powerlink

Second of all, i tried a bunch of tests....
I started playing and watched the thermometer and see when it will shut down... since there is no thermometer for video card i watched only the higher one.. and i noticed that it shuts down around 58-59 degrees (made only 2 tests with the game on)... then i tried to reach the same temperature but without the game.. and see if it shuts down... well i opened a hole bunch of programs,... made different operations, and managed to get the processor to 62-63 degrees... and no shutdown... So now i can rule out the processor overheating...

I still have my doubts about my video card... now i talked to a friend to borrow his video card an see what's happening...

About the PSU... i don;t know if it's any problem... because its very cool and dry... and i can leave my computer on for days even weeks (which i often do... ) and it will not shutdown or reboot and work on it for days (retouching photos, i;m a photographer) and no shutdown... only when i want to play..
I play between 1 min and 15-20 min... and the Baaam... it shuts down..

by the way, i don't' seam to find the temperature of the video card with the ati tool

When you;re playing a game, it will draw more power form the Videocard under load, so if it draws beyond what you;re PSU can handle, then it will crash like it is.

That is why it isn't doing it when it's idle, because its only drawing an idle power load from the graphics card, as soon as the video card needs more power, it crashes.

Yeah, but it should've drain more power first thing i start the game.. so that it shuts down immediately... but sometimes i can play as long as half an hour...

I have a new info... so i put my friend's video card... and i must say that it shut down the same way my video card did... but this time it didn't even booted all the way... i mean, it appeared "Widows is loading" ... then the desktop appeared and shut down...

What do you think guys?

Try another PSU. Borrow your friends if you can.

Are both video cards the same brand...eg. both nVidia or both ATI?

Because it could also be a faulty driver. Especially if it freezes/crashes during Windows desktop loading.

Download Prime95 to check your computers memory as well.

Years ago my old system did this sort of thing and I had 1 bad 512mb stick of ram.

http://files.extremeoverclocking.com/file.php?f=103

Seams that i found a way... i under clocked my video card.... i Put the Core to 100 and memory to 80 with the ati tool.. and managed to play a game no problem for 2 hours and a half...

Looks like your video memory/controller might be marginal. One thing else you might try with the vid card clocks set to default:

If your BIOS settings menu has an option called something like:

Spread Spectrum Enable

Ensure that Spread Spectrum is turned off.

Enabling the spread spectrum EMI "fix" tends to aggravate cards and components with marginal timings, and can cause intermittent failures of this type.

Turning SS on tells the computer to vary the clock timings while the computer is running. This is done to mask EMI standards compliance failures. It's kind of a way to comply with government standards without actually complying with them.

Turning SS off tells the computer to provide stable clock frequencies instead.

I think your video card is just overheating.

Especially if lowering the clocks makes it run stable.

It is an older card, so I am guessing heat is your problem.