New
#11
Ok, despite some of the QUESTIONABLE advice in here, I'll explain what happened.
You installed a new OS. Thus, all your secondary support software (such as QuickTime) is no longer installed. You need to REINSTALL it.
But this brings up a bigger question... how is it that you didn't know this? Do you expect that when you install a new OS it will know how to open PowerPoint files without installing Office? Or that it will know how to work with .PSD files without installing Photoshop?