La fiche KB de référence à bookmarker :-)

Windows Server System software not supported within a Microsoft Virtual Server environment
http://support.microsoft.com/kb/897614/en-us

Il est préférable de lire la version US qui est plus à jour.

A noter concernant ISA Server :

  • Microsoft ISA Server 2000 : ISA Server 2000 is currently not supported running within Virtual Server. 
  • Microsoft ISA Server 2004 : ISA Server 2004 is currently not supported running within Virtual Server. 
  • Microsoft ISA Server 2006 : Microsoft ISA Server 2006 is supported within a Microsoft Virtual Server 2005 R2 environment