log off domain onto workgroup lockd out

I have a client machine(notebook)running W XP Pro. He logs onto a domain at work. He wanted to set up a home network and share the printer connected to his home desktop with the work notebook. I went into system properties/computer name clicked on change selected workgroup and gave it the name of the home workgroup. It then said I would need to reboot. After the reboot it comes up to the ctrl+alt+del scren to log on and then to a log onto windows box with the same name as the user would log onto the domain at work. The password he uses to log onto the domain at work does not work. It appears as though it is looking for a windows user and password that he never remembers having to use.