I just bought a PC on ebay and it works fine except that it restarts randomly when using the internet. My wife used it for several hours straight offline without a problem but when its connected to the internet it just turns off and back on just like someone pulled the cord out of the wall and plugged it back in. Sometimes after restart it will almost completely load then restart again. Sometimes I can use it for 20 or 30 minutes online before it restarts, other times it will only be maybe 10 minutes. Its a celeron D running XP pro. As far as the hardware details I'm not really sure at this point. Unfortunatley the ebay seller is kind of a jack *** so I don't even want to deal with him for return. I have an extended warranty but the warranty don't start for 60 days. Maybe someone here can help me fix it.

Hi doggerdan,
Take a look at this :
http://support.microsoft.com/kb/316416/en-us

I'll try that. One silly question, what is the purpose of safe mode?

Safe Mode is a "clean" working environment that allows you to remove and configure drivers and software - i.e: the drivers are not loaded/used in safe-mode.

Yup , but in this case , and i think Doggerdan means that aswell , i dont have a clue why MS would instruct people to go in safemode to clear the "automaticly restart" check box..

I've disabled automatic restart, but now instead of restarting it just shuts off, no blue screen.

Seems the driver of you networkcard/modem is corrupt. Go the safe mode and completly delete the networkcard/modem through devicemanager. Then restart the pc and reinstall the networkcard/modem with the newest driver for it. Try to download that one if you have another pc.