Microsoft Virtual PC 2007 has already had millions of people download it.  Now, to update the product, Microsoft is releasing a service pack to update the product to the latest and greatest Microsoft operating systems.

Additonal Guest Operating System support:
Windows Vista® Ultimate Edition with Service Pack 1 (SP1)
Windows Vista® Business Edition with Service Pack 1 (SP1)
Windows Vista® Enterprise Edition with Service Pack 1 (SP1)
Windows Server® 2008 Standard
Windows XP Professional with Service Pack 3


Additional Host Operating System support:
Windows Vista® Ultimate Edition with Service Pack 1 (SP1)
Windows Vista® Business Edition with Service Pack 1 (SP1)
Windows Vista® Enterprise Edition with Service Pack 1 (SP1)
Windows XP Professional with Service Pack 3

Download:

http://www.microsoft.com/downloads/details.aspx?FamilyID=28c97d22-6eb8-4a09-a7f7-f6c7a1f000b5&displaylang=en

Release notes:

http://www.microsoft.com/downloads/details.aspx?FamilyID=9f3d3eb5-5e03-4712-999c-e96f91bdf128&displaylang=en