Windows XP user account dialogue empty

I installed Windows XP professional and during setup gave a password for the administrator account and it asks for your name so I gave it that, but did not setup a password for the user account, but it is also an administrator. All normal stuff. I was trying to setup my satelite connection and it kept failing. After some looking the problem is that a user account couldn't be created. If you go to control panel and click on user accounts, it is an empty box. No add an account, change account, etc... Does anyone have any ideas how to repair this or can I reinstall XP over the top of it without loosing data?