Power goes off in PC after sometime

[neelay1]

Hi all, I am a new hardware enthusiast and I just assembled my first PC about 3 months back. Now, all of a sudden, one fine day, my PC just powered off on it's own. After some initial troubleshooting, I noticed that when I power it on, it begins booting, but the keyboard doesn't seem to work (Num Lock stays on) and after sometime (about a min or so), it seems to power off - all fans stop, display also goes off and only the front power LED remains on. First, I thought that there could be something wrong with the power supply (since the fans are directly connected to the power supply), so I replaced the power supply with a new one but the problem still persists. Any idea on what could be wrong?
Help will be highly appreciated!

Thanks,
Neelay.

 

[Tmagic650]

Your CPU may be overheating, CPU fan may be bad , or your motherboard "thinks they" are... Check these things

 

[mailpup]

Start by listing your PC parts specifications including your power supply (old and new). When it powered off on its own, what were you doing on the PC at the time?

 

[neelay1]

When it powered off for the first time, it was only playing music.
Here are my PC specifications-
1] Motherboard: Mach Speed P4MSD-800 D2 Socket 775 Motherboard
2] Processor: Intel Pentium D 940 3.2Ghz DT 800FSB Socket 775
3] Memory: 2 x Ultra 512MB PC4200 DDR2 533MHz
4] Hard Drive: Maxtor 160GB Serial ATA HD 7200/8MB/SATA-3G
5] CPU fan: Masscool Intel Socket 775 Copper Core CPU Fan
6] The case has 2 120mm fans and 1 80mm fan.
7] Old power supply was 450W and the new power supply is 580W.

 

[Tedster]

check your PSU also:

https://www.techspot.com/vb/topic55506.html