My Computer Has No Sound!, Please can someone help? Options

[crazy cow]

Just attempted to play some stuff on windows media player, the speakers appear to have stopped working, then tried on audacity (which I've just downloaded - any connection?) which also doesn't work. I've checked that the sound isn't muted and the speakers are actually turned on (and turned up!) and played around with the balance thing, but to no avail (IMG:style_emoticons/default/sad.gif)
Just about to try with headphones plugged in and see if that works, but in the meantime if anyone has any ideas could you let me know? It was working fine last night, I can't understand what I've done to it!
Thankyou,
hoxie
xxxx