If you're interested in using VSMT (Virtual Server Migration Toolkit) for migrating a physical machine into a virtual machine, there was a new KB article posted up a few days ago which gives you some general guidelines. Note that there is one error in the article - it currently says it applies to Virtual PC 2004. This is incorrect (and I've submitted feedback). It actually applies to Virtual Server 2005.
If you want to see the VSMT steps through a series of blogcasts, have a look here . Thanks to Kevin for giving me the link to the KB - it was one which had slipped me by.