I did P2Ving a 2003 Domain Controller 1 year ago for a client that needed his PDC in a Test env. and I did have a couple of issues but for a Test env. only it can be done.
After the P2V, you will have to run DCDIAG.exe and NETDIAG.exe to make sure everything is up and running. Also, do this trick to make all de previous hardware devices viewable in the Device Management console. Then delete all remaining drivers that are not usefull to VMware (make sure you know what to delete).
http://support.microsoft.com/kb/241257
But there is one MS function that will be broken and it's the SYSVOL and FRS synchronisation within AD.
To resolve this issue, follow this link :http://support.microsoft.com/kb/290762
Other than that, your DC should be working fine. But as always the better way to do it is to create a new DC but sometimes it's not possible.
Bye