Lost sound on HP Pavilion w/Windows XP

[Poker Clif]

I think that someone messing with the sound uninstalled something that I need. It says that I have "no sound mixer" and "no audio device". There is no longer a volume (speaker) icon on the taskbar.

I have checked all of the connections, and went to Windows Update to see if it would automatically download whatever I am missing. I think what's gone is the program "Realtec Audio", or something similarly spelled.

I don't want to reinstall the entire operating system and wipe out all the files currently on my hard drive, just to get this one missing piece back. And I sure don't want to call Microsoft Tech Support, where the first instruction is to get out your credit card.

Any help would be appreciated.