Rebuilt my computer, new motherboard, processor, HD, and memory. I have a valid version of Windows XP Professional for Refurbished PC's with COA. When I installed everything was fine until it wanted to reboot computer to start windows. Then nothing happened. No windows start up. I check with windows compatibility to confirm all my components were windows compatible. I've done the install twice still nothing. I've even disconnected all the other components. Any ideas?