unable to delete old user account on XP

i started a new user account on XP as my pc was getting slow. i have done this before in the past but this time i have trouble deleting the old account. it seems to have deleted most of the contents but i am still able to log in to a bare desktop. The problem is that when i go to user accounts and click on "delete account" the window freezes and eventually i close it with an "end program" box as it isn't doing anything.
Any thoughts?

Cheers