oaklandsit,
I have had this happen to me several times in the past. My machine used to be win98, and it happened several times a week. I then wiped and reinstalled W2k, and it still has happened once.
Each time it happened, all i had to do, was go into device manger and remove the sound devices from the system, reboot, and let plug and play do the rest.
After that, the sound came back good as new.
As i think about it, it did "appear" to happen one other time with W2k, but that was when one of my kids accidentally plugged the left speaker into the subwoofer output of the powered right speaker, instead of the left speaker output. gotta love them kids ehh?
Anyway, try this, and good luck.