I posted a note a while back about what machine I use to demo from. One add nice piece of technology Microsoft has in Beta at the moment is Live Mesh. You can access the site here http://mesh.live.com .
This technology enables you to have a cloud back synchronization mechanism to sync files between machines. The other really awesome feature is the ability to remote into those machines. It has a good application to saving you some setup and not having to always travel with and external hard disk to demo from the VM.
I recorded a note on what you can do with Live Mesh to access a machine back in your office that is running the demo VM.