No Sound after Hard Drive Format

I recently reformatted my computer, and have been unable to get any sound despite having installed all of the drivers.

I'm running Windows XP Professional Edition on a Dell Dimension 4600 desktop computer. My sound card is a "SB Live! 24-bit"

I ran the DirectX Diagnostic program, as well as the diagnostic program that came with the sound card...both failed to detect a problem with my drivers, etc.

Nothing is muted that I can see, the headphones are plugged into the right jack, Windows HAS started the audio service, and I checked to be sure that the sound card in question is set as the default audio device (it is)...I'm 99% certain that there's nothing wrong with the sound card, as it was working perfectly before I formatted the Hard Drive.

I feel like there's something obvious that I'm missing, but I can't for the life of me figure out what it is.