Windows 7 Anytime Upgrade is a great, cheap way to upgrade to Windows 7 Professional or Windows 7 Ultimate.
If your new computer came with Windows 7 Home Premium, but you miss some programs that ran on your old Windows XP computer and not on your new Windows 7 computer, all is not lost.
Windows 7 Professional and Windows 7 Ultimate include the right to download Windows XP Mode from Microsoft and ability to run it. Windows 7 Home Premium, and of course, Windows 7 Starter, won’t run Windows XP Mode.
What’s Windows XP Mode? It’s a special "virtual computer" program that includes a licensed copy of Windows XP Professional. It can be run under Windows 7 Professional and Windows 7 Ultimate, in order to let you use old programs that simply won’t run under Windows 7 any other way.
Another reason for upgrading to Windows 7 Professional from Windows 7 Home Premium is if you need to connect to company networks or other organizations that use Windows domain controllers.
Where can you get it? Microsoft provides an easy link to buy it from them via a link on the Start > All Programs list. But, you can get much better pricing on Windows 7 Anytime Upgrade at Amazon.com.