There are other websites that describe this in detail. Windows 8, 8.1 & 10 Hints (Updated May 17, 2017) IMPORTANT: Anyone with Windows 8.0 or Windows XP needs to immediately update it, to defend against the latest ransomware attack. You will still need to do a trick by not using the regular installer, but do a custom install. QuickTime for Windows has been desupported by Apple, and Apple recommends that Windows users uninstall QuickTime.

If this is about other software suggesting to install QuickTime for its own codec support, then you can install just the “Essentials”, without the Player software.

If you are going to install it against advise, you will have to perform some tricks on later Windows versions.

About QuickTime 7.7.9 for Windows - Apple Support OS Apple stopped developing QuickTime for Windows in 2015, and advises users to uninstall it. QuickTime Player 7 was for Windows 2000, XP, Vista and 7. If it is installed, then this important alert applies to you.Apparently you do not have a running version of QuickTime Player there, from which you can access its menu. The Pro version is also free for basic operation but requires the purchase of a license key to use the full program.

The player comes pre-installed on all Macs and Macbooks and can be installed for free on Windows computers directly from the Apple website. If you upgraded to Windows 8, 8.1 or 10 you may need to ensure that Quicktime for Windows is not installed. Quicktime is a free technology that is standard across Apple and Mac products.

This issue should mainly affect Windows users on Windows 7 versions and below.

Apple will not be issuing any updates (at this time) to fix those vulnerabilities.

There are reported to be at least 2 known zero-day vulnerabilities that directly affect Quicktime for Windows. I posted this here because (1) It's a very important security vulnerability and (2) It's the right thing to do, people need to be at least informed. I routinely receive security alerts daily from the US Cert Program (Computer Emergency Response Team), and I ran across this one this afternoon:

Quicktime windows 8.1