sound card problem

so we have a hand built computer on our hands here, and we had to take everything out to change a power supply. and now after we put all the peices back into a new case, the sound doesn't work. we tried everything, every possibility for the sound card cables, but still nothing. we even went out and bought a new sound card with a whole new set of drivers, and still the shit doesn't work. when we try to play sound a msg box will come up saying

" The volume and mute hot keys do not work because there
is no functioning sound device installed on this system."

and a similar box comes up when we try to play something through a media player (winamp, real player, etc).

Im thinking that the real problem is in the set of drivers but what do you guys think. and if it is the drivers what should i do?