I have a HP Pavilion 473.uk PC using Windows XP, and I got no sound from my powered PolkAudio speakers. I checked for any conflicts in the Device manager under Sounds and it appears fine. I made sure the 'out' jack is in the right (green) socket, enabled Audio Codecs in the BIOS setup (though it was on auto), shut down the computer and uplugged it from the back, and pressed in the power button for 20secs but I still have nothing.
another possibilty is youve selected 5.1 (or other sound out)in the sound software panel (generally listed in all programs>"whatever programme",ie-creative audio Hq.. run through that to select 2 speaker out. another item to try is turn off the system unplug the speaker out lead from the unit turn them on & hold your fingers across the tip of the audio plug ,advance the volume you should hear a load buzzing. telling you the speakers work & yopu need to look else where for the fault (like having the sound out put through headphones on CD.this cuts the sound card out of line.. or the sound card input is aux instead of Line..all need checking.
Under the volume tab it says no Audio Device and hence forth Device Volume and Speaker settings are both greyed out. Can't play no system sounds under the Sound tab. The options under Audio is greyed out as well as Voice.
I had the same problem,and not knowing a lot about PCs i mucked about for a week before i changed my default device in play back,from (modem 0 line play back),to Creative Sound Blaster PCI,and the same with (default device recording) to Creative Sound Blaster PCI. and the sound was restored,dont know if this is any good to you, you can always have a look and see.