The Specified account name is not a member of the local group

From: Eric Vtiale (anonymous_at_discussions.microsoft.com)
Date: 09/30/04 

Date: Thu, 30 Sep 2004 06:12:43 -0700

I installed windows 2000 server. I added a user then
added that user to the administrators group. I now want
to remove the user from the administrators group, so that
it is just in the users group and I get this error....

The Specified account name is not a member of the local
group.