Well a virtual PC would be ideal as a play around but im pretty certain that all virtual pc software doesn't support 3D acceleration so you wouldn't get vista aero working.

To run a virtual pc, just create a new virtual PC run through the set-up wizard, if you want to store it on your external hard-drive, specify it too. To install the OS just run the virtual PC with the boot disk in.

If your not to sure on what ive said, tell me the software your using and i will better describe it.