Computer restarts before boot finishes.?

Boot to the installation CD, go to the Recovery Console, and type fixmbr at the command prompt. Answer "Y" when it asks if you want to rewrite the master boot record. Reboot to the installation CD again, go to the Recovery Console, and type chkdsk /r. Let check disk run, reboot, and all should be good. Note: You will need to know the admin pword you used when installing the OS to get into the Recovery Console.