I recently signed up for a class for windows 2000 professional. When I arrived for the class it was for XP professional. I am pursuing a MCSA and both are good for the os portion. However I am wondering if I would be better off studying 2000 instead?

There are enuf similarities between XP and 2000, but XP is more for coprorate use. If you are planning on administering servers then you really want 2K.