Itunes and Quicktime are both garbage. Neither was meant to run well in any version of Windows, since they were both built for Mac. I can't tell you how many times that stupid apple upgrader has screwed up and F**ked both my itunes and Quicktime installs, to the point I have had to uninstall them, restart, reinstall them from the website downloads, and then restart again. What a PITA! I don't know if this will work, but you could try the Video Lan Codec (VLC) Player. It works great for everything else including DVD's and Blu-Ray.