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.