Sound problem with WMP 11?

I have used WMP 11 for ages with my 5.1 speakers, but recently i noticed that sound is only coming out through the front speakers, left and right, but if i check the sound settings for my pc its set for 5.1, the cables are all in, and even if i play a song with VLC the sound is in all speakers! It's driving me mad trying to figure out why it is doing this and i cant find any specific speakers menu in WMP! all help appreciated, Thanks!