I have Dell desktop pro, Windows 2000, each time i go online, within a few seconds, just long enough to start loading a webpage the computer shuts down and restarts suddenly.  I have run my VirusScan both in REGULAR and safe mode and nothing comes up wrong.  My fans are working so i don't think it's overheating.  What else could it be?  thanks for any help.Much more info will be needed here...
What protection programs do you have...have you ran them all ? ?
How old is the machine ? ?
How do you know all the fans are working ? ?
What happened prior to this ? ?
Installed any new hardware/software LATELY ? ?Much more info will be needed here...
What protection programs do you have...have you ran them all ? ?
How old is the machine ? ?
How do you know all the fans are working ? ?
What happened prior to this ? ?
Installed any new hardware/software lately ? ?

......
protection is macafee virus scan, corporate edition w/online updates
the machine is refurbished recently from a school, circa 2002
I can see and feel the fans blowing..(2)...
a friend had downloaded a couple of apps, corel draw, DREAMWEAVER and a upgraded version of ADOBE acrobat and everything worked fine for about 2 weeks time.
tried switching sockets and using different modem cards, but same thing happens regardless.  I know the modem was working because I switched it into my son's computer and I have no problems with it,  thanks