Since its release in 2006, the Microsoft™ Vista™ operating system (OS), successor to XP, has arguably received a lukewarm reception. Whether due to the widely reported…

http://www.wisegeek.com/whats-involved-in-switching-a-laptop-from-vista-to-xp.htm

Depending on your hardware and your current edition of Windows Vista, you can use the Upgrade option during Windows 7 installation to upgrade from Windows Vista to a corresponding or higher edition of Windows 7.

Upgrading is the most convenient way to get Windows 7 on your computer, because it keeps your files, settings, and programs from Windows Vista in place…

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http://windows.microsoft.com/en-us/windows7/help/upgrading-from-windows-vista-to-windows-7