No Sound - Urgent Help Needed

Well, I've been doing without sound on my Compaq laptop for around 3 weeks
now, and I simply can't put up with it any more. It causes too many problems.

Before this major problem occured, sometimes my computer would be a bit
temperamental and stop the sound coming through, even though it recognised
there was meant to be sound there, and a restart would usually sort it.
However, one time 3 restarts didn't solve the problem, so, in my usual "Oh
I'm a 15-year-old whiz kid I can handle this" manner, I went to the Control
Panel in order to look at the devices that were there.

Speakers, OK. I took the most logical step I could think of in disabling
them, leaving only SPDIF Interface (Conexant High Definition Audio) in their
place. Now, this thing (whatever the heck it is) seems to recognise that
sound is due, but nothing happens! I've looked everywhere I can think of in
my Control Panel for where the speakers have gone, and I even tried a full
system reboot, which didn't work for some reason or another.

Please help, I'm a student and sound really comes in helpful sometimes!! Oh
and uh..go easy, I know I've probably made a fatal mistake, and believe me
when I say I've had all the *tsks* I can take from my mother. Eternally
grateful xx