Before you uninstall
If you're using a QuickTime 7 Pro registration key, you might want to save the key before uninstalling QuickTime 7. It's in the Register tab of QuickTime Player preferences (Edit > Preferences).
If you're not sure whether a program requires QuickTime, contact the program's developer. Most recent media-related programs for Windows – including iTunes 10.5 or later – no longer use QuickTime to play modern media formats. These programs either play the media directly or use the media support built into Windows.
Uninstalling QuickTime 7 also removes the legacy QuickTime 7 web plug-in, if present. Websites increasingly use the HTML5 web standard for a better video-playback experience across a wide range of browsers and devices, without additional software or plug-ins. Removing legacy browser plug-ins enhances the security of your PC.
How to uninstall
Uninstall QuickTime 7 from Control Panel, as you would other programs on your PC. When following Microsoft's instructions for uninstalling programs, choose QuickTime 7 as the program to uninstall.
Or use Windows Search to find 'Uninstall QuickTime', and start the process that way.