My computer hangs on booting. How do I figure out what is going wrong?
This often occurs due to a network/domain issue. Are you logging in to a domain? If so, try logging in to the local machine as the local administrator. If everything boots up quickly, then the problem lies on the network and we can go from there.
A better explanation is that XP isn't very smart with networking. When you log in to your domain, XP tries to make all of those connections to your domain while it is logging in, and waits a very long time before timing out to let you continue to log in.