Group,
I'm running XP on a pentium 4 HP Computer. Sometimes without notice windows re-starts. Any ideas of how to stop this?

Steel[color=purple][/color][face=Arial][/face]

   How does it restart?  Does the whole computer shut off suddenly and then start?  Or does Windows shut down first?  Do you get an error message?  Is there any thing that you do before it restarts?

Windows doesn't shut down first. The screen goes black and it re-boots. One time I left the room and when I came back, it had re-started. I don't get an error message. I wish I did.

Steel

   My guess would be that it is the power supply.
   Usually when the power supply goes bad, the computer just stops working and does not do anything when you push the power button.
   But some times it does what is happening to you: it runs until something in the power supply gets hot and then it shuts off and starts up again.  I don't know of a way to test the power supply for this.  The easiest thing to do is to replace the power supply and see if that solves the problem.
   Power supplies are not hard to replace on desktop computers (I have never replaced a laptop power supply and so the instructions here do not apply to laptops).  If you can open the computer case, you can replace it.  Unplug the computer.  Take the cover off.  Take out the four screws on the back of the computer which hold the power supply in (the power supply is the box which has a fan in it and into which the power cord plugs).  Pull out the power supply box.  Disconnect the connectors and remember where they were connected.  There is one main connection to the motherboard (newer power supplies may have a second, smaller connection to the motherboard too), and connections to each of the devices which need power.
   You can purchase a new power supply at most computer stores.  Newer power supplies will usually work for older ones (not always true the other way around), but you probably should take in the old power supply with you when you purchase a new one to make sure.  The wattage (for example, 400 watts) corresponds with how many connectors there are to connect components like hard drives to power.  Older ones have fewer connectors.

I think your right Ray. I've noticed the fan coming on more often and being louder. I'm going to go ahead and replace the power supply and see if that takes care of the problem. Thanks!

I have the same problem, but am sure it has nothing to do with my power supply, as i get none of the symtoms mentioned. It happens quite often, usually some hours after Windows has shut down. I believe it is due to a problem in Windows XP Pro. I ahve only one task csheduled

I have tried using Bootvis to cure both this and slow booting up, but Bootvis can not complete it's tracing activity, complaining that the disk cannot be defragmented. Neither Windows defrag nor Diskeeper will work, saying that their service can not start. I have checked all the permissions I can think of, and used Windows Installer CleanUp, but found nothing relevant to clean.

Has anyone any ideas?

Thanks