Firefox and WMV Files

When I attempt to view a WMV file from Firefox, it always starts Kaffine which doesn't seem to work with WMV files. I downloaded MPlayer and that seems to work with these files, but how do I get Firefox 1.5 to run MPlayer instead of Kaffine when I click the file link? FWIW, I'm running SuSE 10.0 and KDE 3.4.2. Thanks -- Bill Lugg Milstar Software Support Peterson AFB, CO