Microsoft Vista Virtual Hard Disk
Do you want to play around with Vista before buying it?
Download Virtual Server 2005 (or Virtual PC):http://technet.microsoft.com/en-us/bb738033.aspx
Download Vista VHD image file:http://www.microsoft.com/downloads/details.aspx?FamilyID=c2c27337-d4d1-4b9b-926d-86493c7da1aa&DisplayLang=en
Launch it and play around in a separate environment without disturbing your system. Like it? Buy it!