Uninstall the driver, restart the system. The try installing the same Windows Vista driver using Windows Troubleshooting. right-click on the driver executable/installer file -> Properties and select the Compatibility tab; click the checkbox before Run this program in Compatibility mode for option and select Windows Vista in the list-down box; then try installing the device driver via Run as administrator.
Resources:
http://www.microsoft.com/windows/compatibility/windows-7/en-us/Default.aspx?type=Hardware
http://windows.microsoft.com/en-US/windows7/Tips-for-fixing-common-sound-problems