Anyone with multiple PCs to upgrade might want to consider taking advantage of a Microsoft TechNet Plus membership. It runs $349 for a 1 year subscription and allows you access to all flavors of Windows 7, Office 2007, and much more. You can use up to 10 product keys per product. Discount code TNWIN7RTM also offers a 25% discount on a new Direct subscription if its still in effect.

http://technet.microsoft.com/en-us/default.aspx