computer freezes when attempt to update windows

I just upgraded my kids computer and when I go to the update page and hit
update, the computer freezes up. Any suggestions as to why this is happening.
I also had to repair xp home to get it to run on the new motherboard/cpu. I
note that the task manager and regedit will not stay on the screen, they
start and then disappear. Not sure what's causing this or if its related to
update problem. Any help appreciated.