Andy contacted us about this as Virtual PC SP1 doesn't support x64 guest OS's.

Steve gives all the answers here:

http://blogs.technet.com/steve_lamb/archive/2008/07/08/how-to-run-small-business-server-sbs-2008-on-a-machine-that-s-already-running-vista-xp.aspx

http://blogs.technet.com/steve_lamb/archive/2008/07/08/how-to-re-partition-a-hard-disk-under-vista-or-server-2008-without-having-to-re-install.aspx