I have win xp PC.last weak am facing problem.am using my PC per day 12 hours. In this time 4 time PC autometic resart. I don't know what is a problem. Can you solve this things

Hi,
Thanks for asking a question here, and Welcome to the site.
A PC that restarts itself sometimes could mean different things. Troubleshooting is required to find the issue.
Many times, not enough RAM will cause it. How much RAM do you have?
256 Meg RAM? Less? Or more?
That would be the first place to look. If you have 512 RAM, then it could be something else. Please post back when you know the RAM number.

Do you get any error messages or things like that?

It could be something simple like Windows downloading updates that require you to restart your PC which it can do automatically.

Sometimes these problems can be caused by a bad driver or other software. XP has an excellent feature that allows you to roll back your system state to a prior point without affecting your data.

To see how to use the System Restore feature, visit: http://www.microsoft.com/windowsxp/u...emrestore.mspx
(Do not confuse this with a Restore CD that may have come with your system, for that WILL remove your data.)

While I've never seen random reboots caused by not having enough RAM, I have seen defective RAM cause these kind of problems.

Microsoft has a very good bootable memory diagnostics that will help determine if your memory is defective. http://oca.microsoft.com/en/windiag.asp

I have the same problem with win2000. I've checked the entire system with SiSoftware Sandra Professional and did not find anything wrong. The memory on board is DDR 400 512mHz 3200 Mushkin. When I replaced memory with the Corsair with the same parameters the computer worked fine for a couple days. Then it worked worse and worse.

Overheating or faulty components will also cause this problem, try to see if your cpu fan is running correctly (fast) and also the power supply unit fan. Is the PC hot to the touch? If you can, I would recommend swapping out the PSU with another to test that.