One additional option, Windows 7 – VHD Boot
http://blogs.msdn.com/b/knom/archive...guideline.aspx
This VHD file is mounted as a virtual disk, you can use it as a normal hard disk drive, but all the data is stored in ONE file. The machine is booted physically (unlike with Virtual PC), so you can only run one at a time, but have the full machine’s power.
There’s a performance decrease of about 3%