WinXP keeps rebooting

User Environment WinXP keeps rebooting
I’m running WinXP on a desktop. Whenever I start the computer I get the following message:

User Environment – Windows cannot load the user’s profile but has logged you on with the default profile for the system. – A required privilege is not held by the client.

Then there is a 30 second timer that automatically shuts down my computer and restarts it only to come back to the same message and another restart.

I’ve tried safe mode, last known good configuration and system recovery but that has not fixed the problem.

I do not have a choice to log into the machine as a different user.