If you own a full or upgrade version of Windows Vista either retail or pre-installed, Microsoft has got a pretty sweet deal. The Windows Vista Additional License program provides the ability to install the same edition of Windows Vista on any other additional computers you may own. The program allows customers to purchase up to 5 additional licenses for PCs they own at 10% off the suggested retail price.

For more details, see:

Purchasing additional Windows Vista licenses
http://windowsvistablog.com/blogs/wi...-licenses.aspx

Ordering Additional Licenses for Windows Vista
http://www.microsoft.com/windows/pro...e/default.mspx