PC auto shuts down (w/o msg) and doesnt start now!!!

[MenTaLLyMenTaL]

The config of my PC:

PIV HT - 3.00 GHz, 512Mb RAM. Win XP Pro. Bought it in December.
Using Champion UPS.


Yesterday, i encountered this problem for the first time -
I started the PC. Opened My Computer, Opera, connected to net. Then with few minutes (about 5 mins) It just turned off - just totally blank and off. It didnt make any noise while shutting down, no closing of open apps, etc. Just the monitor went black and the cpu off. So i trie to start it again by pressing the power btn on the CPU. But it did nothing. Then i switched OFF the UPS and again ON. Then, w/o presing the power btn of the CPU, it started! I thot it was a minor problem and again did the usual chores like connecting to net etc. But again wthing few minutes, it shut down the same way. I then checked for any loose contact. And again, had to start the computer by switching UPS OFF and ON and then the computer wud start w/o pressing the Power btn of CPU. This happened like 3-4 times total. Sometimes it would shut off even while starting, without the monitor yet getting to its senses. So once i presses [DEL] to enter the BIOS while starting. But even when i was in BIOS, it shut down withing 2 mins.
But on the 5th (maybe, dont remeber exactly) try when it started, it stayed on. Then I played like usual and it was on till today morning 7.30 (scheduled downloads).

Today, after coming from college my sister told me that she got the same problem of shutting down within few minutes, and it wont start again.

I tried turning UPS OFF then ON, it started automatically. I pressed [DEL] to enter BIOS. But again, it shut down withing 2-3 mins. And then, it wont start now, no matter if i turn OFF/ON the UPS or press or not press the CPU button. I had made absolutely no changes to the BIOS anytime. I was just seeing it.

Also, what could this problem be of - software or hardware?

[mohit]

its mostly a faulty/cheap smps problem. make sure u have a good branded min 400W smps. go for brands like Antec, Colorsit , Powersafe , Zebronics. Also your UPS company looks new and notorious to me. Never compromise on protection and power equipments. Get a good UPS also like APC.

[defconfor]

may be the temp is above the recommended

[MenTaLLyMenTaL]

I dont know what brand's SMPS i have and how watts it is. How do I check it? Will I have to open the cabinet to check?

Also, this cannot be any virus problem na? I dont think so coz the PC doesnt even start.

EDIT: er i obviously i cant check info about SMPS w/o opening the cabinet as the pc isnt starting only. But can u name some tools for that?

[eddie]

There can be several problems.
1) High CPU temps: Check the CPU fan is running and is not full of dust.
2) Failing SMPS: Check with another SMPS. Call your system vendor for one.
3) Voltage fluctuation: Low quality UPS is not being able to handle the fluctuations. Does UPS switches off with the PC? Does monitor's LED goes off as well? If yes then it is UPS
4) Earthing problem: Touch some metallic part of your cabinet with a electricity tester for current. If you see the LED glow, call the electrician.