Using the Windows version of QuickTime 7 is highly discouraged by security experts because Apple stopped providing security updates for it in 2016.
If you previously purchased a license and need to re-activate it on an older system: buy quicktime pro
Are you trying to perform a (like converting a file or recording your screen) that you used to do with QuickTime Pro? QuickTime Pro 7 - Technical Specifications - Apple Support Using the Windows version of QuickTime 7 is