If its definately not your speaker volume/plug or loose/bad cables then it sounds like your sound card isnt installed physically on your system. Cards can be really awkward to slot into some motherboards, and what can look like a really solid fit may still count as not secure when booted up. Switch pc off, take the card out again, and try reinserting. You really have to force some cards in to get them to fit, but try not to be too violent! Make sure your built in sound is disabled and if youre using xp that the 'new card/device detected' message crops up before reinstalling the cards sound drivers.