Mr Bink has all the details, and here is a list of the OS’s that are updated:

 •  Windows Server 2003 with SP2
 
•  Windows Server 2003 R2 with SP2
 
•  Windows Server 2003 x64 Editions with SP2
 
•  Windows Server 2003 R2 x64 Editions with SP2
 
•  Windows Server 2003 for Itanium-based Systems with SP2
 
•  Windows XP Professional x64 Edition with SP2 

 some may be suprised to see Windows XP Pro x64 edition up there, but thats correct. XP x64 is based around a 2003 server core, because of its 64bitness.