XP restart problem

I have XP Home edition. Every time I start up XP, 7 mins(exact) later, the computer restarts and it does the same over and over. I already unchecked the box that says, "restart windows if errors occur." I scaned the system for viruses and checked the reg but it still restarts. After it restarted, XP said that Windows encountered an error. After it displays that, the screen goes blue and it says that windows encountered an error and needs to restart. I already tried system restore and it dosen't fix the problem. HELP!!!