Question : Problem: Why isn't my sound driver loading?

Adcording to My Computer Device Manager, the Multimedia Audio Controller is not installed (yellow triangle with exclamation mark).  The error is code 28.  I don't have the original CD with the HP 5100 computer which is about 4+ years old, so I downloaded from Device Detective.  When I try to load using Hardware Device Wizard, the flying files appear to indicate everything is OK, with the files for Realtek AC'97 seeming to be saved OK.  At the end, the yellow triangle next to Multimedia Audio Controller disappears and the computer self-shuts down.  However, on restart it is just back to where it was, and I can't play any sound.

Answer : Problem: Why isn't my sound driver loading?

your hardware can be bad; test it by running the live Knoppix cd - you should hear the welcome sound :
ftp://ftp.kernel.org/pub/dist/knoppix/KNOPPIX_V6.0.1CD-2009-02-08-EN.iso