Have you rebooting since you installed the driver?
If you have and still have this problem, check the manufacturers website, and go to the support area, and look under FAQs, or 'common known issues'
Also, did you have the audio working before?
Intel E6750...........PSN: ELBATROP
XFX nForce 650i Ultra
Patriot PC2-6400 8GB (4x2GB)
36GB WD Raptor
Samsung SyncMaster 931c
Samsung SyncMaster 750s
Windows 7 Home Premium 64