VIA® P4M266A is not a motherboard brand or model, it's a VIA chipset that can be used on numerous motherboards including the Asrock M266A motherboard. AMI is a bios maker...they have nothing to do with building the motherboard.
Until you can identify the mb. and manufacturer along with the sound chipset number, all I can suggest is to try the sound driver from Asrock here:
http://www.asrock.com/mb/download.asp?Model=M266A&s=
or
http://members.driverguide.com/drive...riverid=142799