[dba-Tech] Linked logins to Windows Server 2003

Dear Group,

The network "guru" that an old client of mine had hired to install his
Windows Server 2003 Enterprise has taken himself out of the game.
Suffice it to say that he's in trouble with the law and probably won't
be returning.

I've taken over as de facto network guy.  I have a horseback knowledge
of Windows Server 2003 and I've learned a fair amount in the past two
weeks.  But I ran into something odd regarding user accounts.

The felon -- I mean the network guru -- had set up a user account for
himself, of course.  I recently changed its password.  But I also
tried to disable the account from the Active Directory Users and
Computers application: Action | Disable.

When I did that, however, the owner of the company could no longer log
in.  When I re-enabled the felon's account, the owner could log back
in.

My question is: what kind of linking can there be between user
accounts that would accomplish this kind of symbiosis or parasitic
behavior?  I want to disable the guy's account but, apparently, I
can't.

Any ideas?

Regards,

Steve Erbach
Neenah, WI