To download QuickTime 7.5.5 for Mac OS X 10.5.8 (Leopard), you can access historical installers through archived community threads and third-party repositories. Recommended Download Links
However, none of these integrate with the system-wide QuickTime frameworks (used by iMovie HD, Final Cut Pro 5, or GarageBand). If you use Apple’s Pro apps, QuickTime 7.5.5 is irreplaceable.
Finding direct official links for these legacy versions can be difficult as Apple has deprecated older QuickTime releases. However, the following resources still host relevant installers: Apple Discussions QuickTime 7.7 for Leopard
QuickTime is a free media player that allows users to play, record, edit, and share audio and video content. QuickTime 7.5.5, released in 2009, is a significant update that brings several improvements, including:
page for legacy software. While it primarily lists versions for 10.6.3 (Snow Leopard) and 7.6.4 for Tiger/Leopard, it is the safest official starting point. Third-Party Archives : Sites like OldVersion.com