PitViper

From Microsoft....

Currently running Windows XP: Microsoft designed Windows 7 Upgrade media for Windows Vista. Customers with Windows XP can purchase Windows 7 Upgrade versions but must back up their files, clean install, and then reinstall their applications.

Currently running Windows Vista: Customers with Windows Vista can purchase Windows 7 Upgrade versions. You can do a clean install (back up your files, clean install, and then reinstall your applications) or an in-place upgrade (Windows 7 installs over Windows Vista).

Link (see bottom of page)

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"I prefer a man who will burn the flag and then wrap himself in the Constitution to a man who will burn the Constitution and then wrap himself in the flag." - Craig Washington