Computer continually restarts itself
i recently formatted my HD, reinstalled windows xp professional and installed a new DVD drive. ever since, my computer restarts itself many times, in different situations:
a. during power-on: almost always restarts a number of times before finally allowing me to work. the restart usually happens a few seconds after the XP logo comes up. I'm not sure, but i think this happens less often when there is no CD in the drive.
b. in the middle of work: the computer randomly decides to restart itself.
what can i do to stop this?