only thing i can suggest is to partition your drive into 3 smaller sections, the middle drive should be in the centre of the drive and the last one should be the centre of the disk. at 7200rpm, the disk is spinning on the outer edge at almost 200mph (yes thats MILES PER HOUR, data courtesy of a feature in micromart). this will reduce the cluster size and maybe make a difference, but i doubt it is what you are looking for.
Cant help with the sound card thingy except to say have you got the latest drivers for the audigy card, and have you been to thier website to see if there is a F.A.Q. section, same goes for the Terratec DMX6Fire soundcard. sorry mate best i can do on this one.