No sound from my desktop

Hello, im new here and i have a compaq desktop computer and it came installed with windowsxp sp3 and i just installed windows vista home basic since i installed vista i havent a no sound from my speakers or head phone on back or front on my desktop i check hardware changes nothing has change i even check for updates on the drivers from device mang and it tell me that my drivers are already installed and up to date and is working i have a A7V8XLA motherboard built in sound card made by realtek i need help if you know anyother good drivers that will work with vista let me know and were to get them