Computer Shuts off After Selecting User in XP Login

Greetings,
So I am having an issue with a computer of mine and am wondering if someone can help. I turned the computer on today and everything worked fine up until the user login screen (of Windows XP). When I select a user, it continues on like it is fine and goes to the “Loading Personal Settings…” screen, but then the computer just shuts off. Has anyone had this problem before, or possibly know what the problem could be?
Thank you