that could be why its not working to begin with. alot of time the onboard audio not only controls the speaker out jack, but whatever aftermarket sc u decide to install. right click on the multimedia audio controler, (the red x) click uninstal, then restart and see if it detects. if it doesnt, open the side of the case and look at the square chips on the board, one should say "via", or "sis" or something simular. then u just goto the manufactures website and dl the drivers from them. although dell makes the pc, they dont make the board, they are manufactured for dell by various companies, such as sis or via. if u open the case, somewhere on the board through all the wireing should be the boards number, usually in larger white print. if the above does not work, post that info here.
P.S. instead of unpluging the battery, there is a small 3 pronged jumper on the board near the battery, if u remove the jumper frome one setting to the other, it clears the bios, which isnt recommended in all except the most desperate times.