In case you haven’t heard, Apple is discontinuing QuickTime Updates for Windows. There are currently known security flaws in it, so you should uninstall QuickTime from your Windows computers. HOWEVER, if you are running Adobe Creative Cloud, you may need to keep it on your computer a little while longer because it will break some features in Creative Cloud. Hopefully, Adobe will quickly address that issue.
HTML 5 should be all that you need for watching online videos. If you are watching DVD’s Windows Media Player should be just fine for your needs.