I have a strange one here. A user has a notebook that used to belong to a domain. A very restrictive Group Policy had been applied (no local drive access, context menus, run dialogue, task manager, control panel). User was given the opportunity to buy the machine when they left their previous company. Machine had not been removed from that domain on exit. One of my technicians helped this user out by changing the local Administrator password, logging on as the local Administrator, and removing the machine from the old domain. The group policy still appears to be in place however and applies to every account other than the local Administrator (even other members of the local Administrators group). An attempt to join this machine to another domain had no effect on the existing policy. The system is running XP SP2.
Note: This is an actual problem that I ran into a couple of years ago. I did not have much opportunity to deal with it at the time so after some basic troubleshooting I took an image of the HD and reinstalled. I have the time now so I've applied that image to a similar image and have turned it into a lab case. I have to admit that I am as stumped today as I was then.