My system persisted in showing a green screen whenever I tried to play most videos.
I tried all the tricks on the web.
Interestingly, I didn't have a way to "disable hardware acceleration" when I right clicked on the videos
So, while trying to uninstall/reinstall my video drivers I figured that I'd check the videos again.
Once the ATI drivers were removed (uninstalled), the "disable hardware acceleration" thing came back.
I unchecked it and my videos are working again!!!
I hope that this tip will help others that are experiencing the same problem.