Installing Win2k3 admin pak on instance of virtual server

I’m trying to install the Win2k3 admin pack on an instance of virtual server but I get the following error message:

“Windows Server 2003 Administration Tools Pack can only be installed on Windows XP Professional with QFE Q329357 applies, on Windows XP Professional Service Pack 1 or later, or on computers running Windows Server 2003 operating systems.”

The virtual server is Win2K3 SP2 on Virtual Server 2005 R2. Any ideas on why I’m getting this error? Fix or work around?