Hyper-V Program Manager
'What Works and What Doesn't in Microsoft Virtual PC 2004' (http://vpc.visualwin.com/) is a great website that is maintained by Jonathan Maltz. It lists all reported operating systems that people have tried under Virtual PC. At this stage there are 715 operating systems listed, 571 of which have been reported to work.
I love this website - and usually visit it on Friday afternoons to look for a new OS to play with under Virtual PC. Much kudos to Jon for his work here - and I think that we can all rest a little bit easier knowing that the 'BEERnix 1.0 Beta' does indeed run under Virtual PC :-)