ya try all of the above,be sure to update the drivers aswell.
Vista has a strange interface for sound and doesn't work well with AHII,that said it's not impossible fix it. For my system I had to plug mic into rear panel and headphones on front panel.
BTW,dont expect the same quality sound in AH with vista,xp has much better sound.
Skuzzy can explain the reasons much better that I.(hands off to Roy)...LOL