At its Worldwide Partner Conference in the US, Microsoft announced the availability of a public beta for Windows 7 and Windows Server 2008 R2 Service Pack 1 and said it would extend downgrade rights to Windows XP Professional.

SP1 for Windows 7 does not contain any new features but there are new features in SP1 for Windows Server 2008 R2 such as an enhanced virtual desktop experience.

“To support our customers’ ‘unprecedented move’ to migrate their PC environment to Windows 7, we have decided to extend downgrade rights to Windows XP Professional beyond the previously planned end date at Windows 7 SP1,” said Windows Communications Manager, Brandon LeBlanc.

“This will help maintain consistency for downgrade rights throughout the Windows 7 lifecycle. As a result, the OEM versions of Windows 7 Professional and Windows 7 Ultimate will continue to include downgrade rights to the similar versions of Windows Vista or Windows XP Professional. Going forward, businesses can continue to purchase new PCs and utilise end user downgrade rights to Windows XP or Windows Vista until they are ready to use Windows 7. Enabling such rights throughout the Windows 7 lifecycle will make it easier for customers as they plan deployments to Windows 7,” he explained in a blog post.

LeBlanc confirming the current policy of allowing retailers to sell the boxed version of the previous OS for up to one year after release of a new OS, and that OEMs can sell PCs with the previous OS pre-loaded for up to two years after the launch date of the new OS.

“This means that since Windows 7 launched on October 22, 2009, retailers will be able to sell the boxed version of Windows Vista until October 22, 2010, and OEMs will be able to sell PCs with Windows Vista pre-installed until October 22, 2011.”

LeBlanc recently confirmed that Windows 7 had sold 150 million licenses to-date.