My system is Compaq Evo D380mx, P4 1.66, Intel 845g, 512MB RAM, integrated AC97 audio, XP-pro SP2, WMP10. The other details from Everest scan (done when system was ok) are :-
Audio Adapter Intel 82801DB ICH4 - AC'97 Audio Controller [A-1]
Audio Controller Type Intel 82801DB(M) ICH4
Codec Name SigmaTel STAC9750/51
Codec ID 83847650h
S/PDIF Output Supported
Device Description SigmaTel Audio
Driver Module STAC97.sys
Driver Description SigmaTel C-Major Audio
Driver Date 02-26-02
Driver Version 5.10.0.3630
Driver Provider SigmaTel
INF File oem4.inf
Hardware ID PCI\VEN_8086&DEV_24C5&SUBSYS_0511147B&REV_01
Location Information PCI bus 0, device 31, function 5

So far (last five years) audio has played smooth. Just had to replace the heatsink fan ... got a technician to do it. After that windows sounds (start / shutdown) did play, and I did not check any music. Later, WMP refused to play music. Device manager shows all ok, but control panel > sound properties > volume says "no audio device". Now, even the windows sounds are not coming.

Thanks for help.