No sound in any of my internet browsers (Firefox, Explorer)...?

So I recently bought a printer at Walmart, and when I installed it, I believed it ruined the sound on my computer. Before I had installed the printer, sound was working fine. However, after installing the printer, I completely heard no sound, so I went to the Dell website (since I own a Dell desktop running on Windows XP). Afterwards, I deleted the IDT driver and reinstalled the original sigmatel driver on my computer and it worked. I now hear sound on my windows media player, Itunes, etc... But, I can't seem to hear anything in my internet browser, though (Mozilla Firefox 4.0). I tried checking to see if I heard any sound on Internet Explorer, and can't hear anything on there either. Can someone guide me in the right direction and tell me what to do in order to get sound in my internet browser? By the way, I have updated Adobe Flash Player and Java. In addition, I've tried downloading a K-lite mega codec, and had no luck either...