In-place upgrade from Windows Vista with Service Pack 1 to Windows 7 with is supported if the processor architecture and the language are the same and their editions match (see below). In-place upgrade is not supported for earlier versions of Windows; moving to Windows 7 on these machines requires a clean installation, i. e. removal of the old operating system, installing Windows 7 and reinstalling all previously installed programs. Windows Easy Transfer can assist in this process. Microsoft made upgrade SKUs of Windows 7 for selected editions of Windows XP and Windows Vista. The difference between these SKUs and full SKUs of Windows 7 is their lower price and proof of license ownership of a qualifying previous version of Windows. Same restrictions on in-place upgrading applies to these SKUs as well. In addition, Windows 7 is available as a Family Pack upgrade edition in certain markets, to upgrade to Windows 7 Home Premium only. It gives licenses to upgrade three machines from Vista or Windows XP to the Windows 7 Home Premium edition. These are not full versions, so each machine to be upgraded must have one of these qualifying previous versions of Windows for them to work. In the United States, this offer expired in early December 2009. In October 2010, to commemorate the anniversary of Windows 7, Microsoft once again made Windows 7 Home Premium Family Pack available for a limited time, while supplies lasted.