I recently installed Windows 2000 Service Pack 4 on my system. Now if I lock my computer for a long duration and then when I unlock it. It restarts automatically. What could the possible problem be? Even if I leave the system idle for a little while and then get back to it, it restarts automatically. I haev checked for viruses and stuff, but found none. This problem has only arrrived after I installed Service Pack 4. Any help??