No sound with streaming media?

Recently I reloaded WindowsXPsp2. Ever since then I am not able to listen to music on internet. When I log on and click play it shows as playing, but no sound comes. Movie clips play without sound. But when I play files from my hard disk sound is present.
Another thing that I have found is there is no volume icon on my task bar. All attempts to get it back have failed. Please advise what is to be done.
BPN