iTunes and 5.1 surround sound problem

Hi guys, i built a new pc with a 5.1 audio board. I have tried installing itunes for a week, but i don't manage to make it work. It gives me an error on a dll file (coreaudiotoolbox.dll) and makes itunes crash. What can i do?

Please help me!

I have windows 7 (64bit) and an ASrock 970 Extreme 3 as motherboard (http://www.asrock.com/mb/AMD/970%20Extreme3/index.it.asp)