Windows XP lets remote registry editing by running a service for it. Below are the step-by-step instructions to disable this security hole:

1. Goto your control panel (you can do this by clicking on your start menu)
2. Select administrative tools - services
3. On the right panel, find the service called "remote registry"
4. Right click on it and select properties
5. In the startup type option box, select disable
6. Reboot you computer and repeat steps 1-4. You should see it won't be running anymore.