VANStudents.COM windows server 2000 native domain
VAN.COM Windows Server 2003 function level domain
VANSTUDNETS\Enterprise Admins is a Universal scope type. 
You cannot add a user from VAN.COM domain even though the Enterprise Admins has the Universal scope.
However, you can add the VAN\Administrator to the built-in group VANSTUDENTS\Administrators, which has the local scope. You can add VAN\administrator user to administrators group of VANSTUDENTS domain's XP computers.
