Once you get the green screen, you've ruined your codecs by recently installing a bad codec, and probably by installing something related to Microsoft - that's been my experience, anyway
![cl_out](/images/eoff_smilies/tongue.gif)
Unless there's an uninstall to get rid of such offending codecs, or you know what to touch in the registry to undo the mess and unregister such codec, or you understand how to do codec overrides for various fourccs etc. at the very least in a single player such as in
Media Player Classic (though that's only a temporary solution), you're stuck and will need to reinstall Windows to clean the mess you made
![cl_out](/images/eoff_smilies/tongue.gif)
Installing more and more codecs to try and get around it is a bad idea.