I built a computer for a friend a few months ago. He said it works great except when he is on the internet, then it hard locks within 5-10 min (you have to hold the power button in and force it to shut down). He said it never locks when he is not on the net. So I thought the only thing different that is being used on the net is the modem. I tried changing it and the problem is the same. Any ideas??? What could cause it to only lock on the net, not when running other programs???