Remove it from "programs and features" then go to Microsoft and get a new one. If this doesn't fix it check your audio it might need a new driver or a settings change. By the way Real Player plays nearly all the formats now, including WMP.
I have a Dell Inspiron 9400 with a T7200 @ 2.00GHz 2.00 GHz processor running Vista. Now when I'm using WMP11 it takes almost 20 seconds to play a song from the time I click play and when the song is almost over it skips 3-4 times then switches to the next song quickly. I don't think my computer is underpowered, but why would WMP11 be doing this? It is really aggravating. Thanks