Always Use The Selected Program To Open This Kind Of File Not Highlighted

If  "always use the selected program to open this kind of file" is not highlighted.

In my case my mp4 and mpg files were not able to be changed to a default program

Go to Start, then type Default Programs, click on Default Programs

Click on "Set program access and computer defaults", click OK to UAC if prompted

Select Microsoft Windows, then click OK

Some files still would not allow file association, for example MP4 files

I ran VLC, then  Tools, then Preferences

Scroll down and click on Set up associations....

Select mp4, then OK or in my case I selected all, then Ok, as i use VLC for playing all media files.

See: http://www.sevenforums.com/tutorials/19449-default-file-type-associations-restore.html for other file types.