dont know about vista havent used and dont want to.
on windows '98 or windows xp you just go to the audio control panel.
on xp and windows '98 when you in the volume control setting there is a view option and you can select what audio options you have control too.
or you could get a sound blaster live or whatever the newest version is of that card and have more access to audio features and effects and stuff to add to them.
I'm using Vista and the sound control panel seems to be lacking the ability to pass through my line-in to my speakers. Does anyone know of a program or hack to get around this? I've searched the net and haven't produced any concrete results.