Hey guys, I was actually reading all your comments in hopes of finding a solution myself. I had the same problem most of you have or had.
I'm running a Vista Home Premium 6-bit laptop/notebook, and my sound drivers/cards are "Avnex Virtal Audio Device" and "Conexant High Definition SmartAudio 221"
There are other two which I found to be useless so I won't name them.
My laptop (gateway) was working perfectly fine until I plugged in a pair of headphones, then all my sound completely went away. I was going insane and thought about unistalling my sound cards and installing new ones, but I'm not good with computers and was going to mess it all up worse, so I decided not to.
Anyway, I couldn't find an answer, and non of yours seemed to work, so I fooled around with them, and finally ended up Making the Conexant speaker the default speakers.
I did this by going to Control Panel > Sound >
And you'll see the speakers there. I had Avnex as my default, so I pressed on it, And pressed Properties. Then I went through all the taps and tested everyone. Non seemed to work. So I went to Conexant and did the same thing. The test worked and I heard some beeping sounds.
My Fiancee next to me asked me why Avnex was the default, and I said I didn't know, it was that way before I did anything, so I got the idea to make Conexant the default drivers and it worked. I started getting the beeping sounds when I get a pop up or something, so I tried my Itunes and WALAH! :D
I thought I had burned down my speakers or something because (being a huge fan of downloads) I have kept my laptop on 3 days in a row now. (the file is huge and my internet is BLAH. *cough* Comcast *cough*) and my laptop has gotten BURNING underneath.
Anyway, hoped I helped. :)