are you using a soundcard? HD audio bus refers to the on board sound. you can turn off on board sound in the cmos. expansion cards such as sound cards use the pci bus.
i have recently installed a new MB and all the installation went well except the audio device high definition bus has a ! on it in device manager. i am using win xp pro sp3 (32 bit) the board is a asus M2N-MX SE PLUS with a AMD Athlon64X2 Processor 4200+ 2.21 GHz, 1.87GB of RAM have installed the newest bios that i could find on the asus web page and tried all the audio drivers available there as well to no avail. i have also tried using ms patch KB888111 but it will not accept it saying that i have a newer version. i am at a lose and have no sound but rest of the system is operating properly. any suggestions?