You need Vista drivers for the sound card. This is the main reason I have not and will not purchase VIsta until After service pack 2, at a minimum, is released for Vista. It is a memory hog and there are very few drivers. We all faced the same thing when MS bumped up to XP from 98SE/ME. XP was buggy until service Pack 2. I would consider, If I were you, putting Vista on the shelf until most of the bugs are worked out. I guarentee you won't have sound card issues with XP. Hold on to Vista until at least Service Pack 1 is released and use for XP for now.
Noli Nothis Permittere Te Terere!!
EVGA 680i, Dual EVGA 8800GT'S (650/950), 4 gigs OCZ DDR2 1066, Intel Q9450 at 3.8 Ghz, Koolance Water Cooled, Dual Plextor16x DL DVD+/-RW. Dual WD 250gb 16mb Cache Sata 3.0. 3DMark06 score = 19,168.