Start up problems

[Ken R.]

I originally was using windows XP home edition, and
recently upgraded to windows XP Professional. I'm
experiencing startup problems. When I startup, I am
allowed to choose which OS I want to use, but when I try
to boot up in W XP Pro, it takes me to the screen right
before the windows screen where you see the users. Its a
black screen with the pointer in it, but the pointer is
not present and it takes me back to the begining where
you choose the OS you want to use. Is this common and how
can I fix this?