Removing and reinstalling iTunes, QuickTime, and other software components for Windows Vista or Windows 7 – Learn how to cleanly uninstall iTunes, QuickTime, and other essential software components from your Windows Vista or Windows 7 PC; (for a Windows XP or Windows 2000 PC, refer to Removing and Reinstalling iTunes, QuickTime, and other software components for Windows XP).

http://support.apple.com/kb/HT1923