computer reboots on itself

Insufficient case or processor cooling could also cause this. Take the cover off your system, and use a room fan to blow air into the case. If the problem goes away, you should probably add case cooling fan(s) and a better CPU heatsink/fan combination.

If the room fan advice fixes the problem, we can post links for good sources of cooling.

A faulty video card can also cause a reboot.  Do you have a video card you can swap out for your current controller?

Actually nowadays, when i login,,,it started crashing more often sometimes with blue screen, it then reboots itself. I am in process of checking video card and IRQ conflicts and so on.
Also, i am thinking of backing up my stuff and reinstall Win2k pro again. Do u think that would help??

If you want too try, use your WIn2K bootfloppy. When you access the Win2K CD to install it will give you the option of repairing your present installion,

Repair sometimes works, but nothing is better than a clean install for cleaning junk left behind in the registry.

I deleted everything from the harddrive and tried to install Win2k , but even while installing, the computer kept crashing. I tested the RAM, Network card, and harddrive, they are all fine. I think it must be motherboard.

Have you tried the additional cooling by use of a room fan?

Go to the Control Panel, then System, then Advanced, then Startup and Recovery.  Make sure "Automatically Reboot" is NOT checked.  Now when it encounters a critical error, it should give you a blue screen instead of rebooting.

Good point.  I had that happen with an NT4 server.  It would just reboot out of the blue.  That was the solution.

That was a good point, but what is the reason for the blue screen. Is it motherboard? Apparently not software ( OS), harddrive, RAM, Network card.

Without the specific error message, it's hard to say.  I use to get IRQL_NOT_LESS_OR_EQUAL errors when I rebuilt my system and used a newer NVIDIA driver.  Going back to the old drivers fixed the problem.  It could be incompatible (not APCI compliant or complaint in general) hardware, faulty hardware, corrupt software (either a driver or some piece of software running on the machine), etc.

You were talking about backing up and doing a clean install.  If you can afford to do so (and then turn off the automatic reboot thing), that would probably be the way that I would go.  Then spin on the basic build for a few days and see if it acts up.  If it does, it's probably hardware.  Hopefully you can get a BSOD with a dump which may lead to the source of the problem.

Happy hunting. =|

Thanks every body!!
Finally found the problem( something hard to find), capacitors on the mother board, they were fried with heat.
I had to replace new motherboard with CPU and all. Anyways thanks to all.
Wish i could divide my points.

Wow, how did you find that?  Just curious.

Look on mobo.  See crispy fried parts.  Not hard, actually.

You can divide the points.  Create a 0-point question in Community Service (link at left) and put a link to this question in it.  Tell then how you want it divided.

Or by smell...I helped one of my co-workers setup his computer.  And then we smelt something burning...it was the processor!  The heatsink grease melted right off the CPU.  And the fan was working on the CPU, go figure.  Never seen anything like that