Windows media Player vs. Musicmatch

I can't stand Musicmatch and want to only use the WMP. I have selected all files in the WMP file types section. When I go to certain music download sites something chamges the WMP file types de-selecting certain ones and then at the music sites the format is Musicmatch. I have to go back into WMP and change the file types selection each time. What can I do to stop this problem??