As you probably know from past posts I am a huge fan of Virtual PC.  I like it better than VMWare because it supports differencing drives and other things that VMWare can not compete.  However there are two things that Virtual PC must add in the next release.  First, the compacting utility doesn’t work all that well but there are work-arounds for that.  Secondly, I don’t think MS realized how much developers are using VPC.  I think it was slated as more of an administrator’s tool.  But this tool is invaluable for developers and especially testers.  If there is one thing I get asked more than anything from testers it is “How can I compare two machines? One works one doesn’t and I can’t tell what’s different.”  Why can’t we have a VPC diff utility that shows the differences on the file system as well as the registry!