No multimedia audio controller driver

Hey i recently upgraded my dimension 9150 from windows XP to Vista Business and i can't get any sound. I've looked in device manager and seen that there is no driver for the multimedia audio controller, i've been to the drivers and downloads page but there's no drivers for vista, i couldn't find the driver for xp either, i tried entering the service tag from the machine and it doesn't even recognise it on the site. Anybody know where i can get the driver for it?

Cheers