Hi a few weeks ago I blogged about recommended best practises of Virtualizing your Domain Controllers environment. I am currently working with a customer on quite a complicated scenario that touches on virtualization and through my research  and pointers from my Colleague Mark Empson have come across an excellent Blog Post posted by  Gavin Mcshera of Premier Field Engineering in Ireland.

http://blogs.technet.com/pfe-ireland/archive/2008/05/08/virtual-domain-controllers-and-time-synchronisation.aspx

Please also find another great collection of links as put together by my friend a colleague Mark Empson and other colleagues Rick Stone and Ned Pyle  all of Microsoft.

KB897615  Support policy for Microsoft software running in non-Microsoft hardware virtualization software

http://support.microsoft.com/default.aspx?scid=kb;EN-US;897615

KB: 897613 Microsoft Virtual Server support policy
http://www.support.microsoft.com/kb/897613

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

KB888794 Considerations when hosting Active Directory domain controller in virtual hosting environments
http://support.microsoft.com/default.aspx?scid=kb;EN-US;888794

KB320220  Support policy for Exchange Server 2003 running on hardware virtualization software
http://support.microsoft.com/default.aspx?scid=kb;EN-US;320220

KB909840  Hardware virtualization support for SharePoint products and technologies
http://support.microsoft.com/default.aspx?scid=kb;EN-US;909840

KB953797  Time Synchronization issue in Windows Server 2003 systems running as VMware Guests

http://support.microsoft.com/default.aspx?scid=kb;EN-US;953797

KB888746  You may experience time-related issues with programs that run in a virtual machine in Virtual Server 2005

http://support.microsoft.com/default.aspx?scid=kb;EN-US;888746

KB887727  Time synchronization settings in Virtual Server 2005

http://support.microsoft.com/default.aspx?scid=kb;EN-US;887727

KBVMware Time Sync and Windows Time Service

http://kb.vmware.com/selfservice/viewContent.do?language=en_US&externalId=1318

KB888794  Considerations when hosting Active Directory domain controller in virtual hosting environments

http://support.microsoft.com/default.aspx?scid=kb;EN-US;888794

Running Domain Controllers in Virtual Server 2005

http://www.microsoft.com/downloads/details.aspx?familyid=64db845d-f7a3-4209-8ed2-e261a117fc6b&displaylang=en

    For pre-deployment of virtualized DCs, you can try the MAP 3.0 tool at;
     www.microsoft.com/map