Vista 64-bit USB Audio Device driver install error

I am in the process of installing software in my new Vista Business 64-bit machine, which uses two Intel Xeon CPUs. This machine was configured by Dell and came with a Sound Blaster X-FI sound card, which works fine.

Today I tried to install a US Interface Navigator device which includes an internal sound card. The Navigator has a USB connection with my computer. I had on hand 64-bit drivers furnished by US Interface, and installation went ok. Following instructions I then connected the Navigator to the USB port of the computer, which sensed several new USB devices and installed them all OK except for the USB Audio CODEC, which the Navigator people tell me should be part of Vista. At this point Vista gave me an error message box telling me that it "found driver software for your device but encountered an error while attempting to install it." Below this it displays an image of a speaker with the words "USB Audio Device". It then states "The system cannot find the file specified."

I have been told that driver software for a USB Audio CODEC is part of standard Vista. Does anyone have any suggestions?
-- John

My problem seems to be solved. I was able to find someone else with a similar system and a working USB Audio CODEC drive. Among the list of driver files for his device was the file USBAUDIO.sys. A search of my system drive found that there were three files with this name, one of which had a date of 2006 and was smaller than the other two files. The two larger files both had a date of 01/20/2008. Note that my computer was purchased brand new from Dell in late September, 2008.

I then proceded to attempt another install, and when the screen came up asking me where to look for the driver, I browsed to a folder in the \Windows\System32\DriverStore\FileRepository\wdma_usb.inf_cb86604b and let the driver installation procede. I was presented with a large red warning that this driver was not signed, but clicked the go ahead anyway button and the installation proceded without incident.

My Navigator device works great, and in Device Manager the location of the device has been moved from Portable Devices to Sound, video and game controllers.