Now this is worth a read having just found about it internally. Megans whitepaper which I blogged about recently is now available in its completed from on microsoft.com. The whitepaper discusses in detail the differences between Virtual PC 2004 and Virtual Server 2005. I know from my own experiences that this is something which many people do not fully understand, not just be those outside of Microsoft, but more often from internal people (who I won't mention my name just to be on the safe side :-)). This paper provides you with all the information you need and can be downloaded here.