Sound driver installation

Hello,

after i installed windows 7 on my acer extensa 2300 laptop, i am unable to install the audio output driver. i installed realtek audio high definition driver. after i installed i got the message saying that the device cannot start. Error Code 10 was also shown. what to I do now.....
also from where can i get VGA and multimedia audio controller for my laptop acer extensa 2300. how can i install it.