Windows Media Player 11 Problem

I recently updated WMP to version 11 and found, to my dismay, that some previous file associations had been altered. Audio files run as before but all video files, when double clicked, try to open with Notepad. In the right-click menu of an .avi file, at the top, is "Open With Notepad" in bold. This is a new item in the menu that appeared after the install. I tried using "Open With..." to select WMP (I checked the box to always use this program) but it will only work the one time. Subsequent attempts to open the file result in the same attempt to use Notepad. Next, I uninstalled WMP, which rolls the version back to version 10, but the same problem exists - as well as the right-click menu item.
Can anyone tell me how to assign a file association that will stick, as well as get rid of that menu item?
Any and all help with this would be great.