Here is a sticky one for you. I upgraded my main XP PRO system to XP2 last year I noticed I had lost audio but did nothing about it as I do not use Audio in normal use. On my return from the USA last week I wanted to put skype on the system which is an ECS K7S5A M/board with an ATHLON 1800XP,
This has a Realtek AC97 inbuilt sound chip. The drivers install fine no nasty yellow triangles but no sound and no Realtek audio device shown in Sounds and Audio devices/Audio . The only audio device shown is the built in Modem. I put in a Creative SB Live 5.1 which installed without trouble but shows fine in Control panel /Hardware Devices but does not work. I tried all combinations of the three audio devices but none would work either singly or together. Investigating control panel/Device Manager/ Hardware/Sound Vid game Contrlrs I came to a box Creative SB live Mixer properties which had a message "driver enabled but not started" The Realtek AC 97 device had the same message The one device that shows in Control Panel /Sounds and Audio is the modem and that has a message in properties that says "Status river is enabled and functioning properly".