You issue maybe SP3
Did you install SP3 before you had ALL your drivers working?
Did you remove your other drivers (Sound) before installing the driver I Posted.
(Remove in ADD/Remove Programs and in the Device Manager)
http://www.mediafire.com/?dg0cmmkm4y4
I can confirm this driver works as I have done several downgrades using this driver and have had no issues, but yours might be the first.