My fears where justified when realizing that clicking on online mp3 files (like almost all on this site) didn't open up Windows Media Player but instead started an IE embedded quicktime player instead. Trying to change the settings within the Quicktime player (regular file association, MIME settings) didn't change anything.
I've found the solution and I'm guessing I'm not the only one with this problem so here goes:
Open up Windows Media Player and open the "File Types" options under the menu "Tools"->"Options". Locate the MP3 checkbox and make sure it's checked and having a white background. (Uncheck and click it again if it's got dark gray background.) BINGO! Problem solved.
Sincerely
LarsErik
PS. Merry Christmas!

