Best of luck...managing many extensions, MIME types and helper applications is a major PITA.
Media players in general are notoriously slimy when it comes to stealing each others' associations (register with Windows so that when you open a file the correct program runs). WMP, iTunes, WinAmp, and that really stinky Apple QuickTime all fight for MP3, M3U, MP4, AVI and other media extensions.
WinAmp is one of the better ones in that at least you are presented with a dialog box at install time asking you what extensions you want it to have.
Anytime you install a new media player or even upgrade one be aware that the app to will probably try reclaim all media extensions so just don't go flying through the various install dialog boxes without reading them - one of them will most likely be the app looking to reclaim all media extensions, which may break your day-to-day media experience.