Using AVD, I successfully obtained the USB driver. I followed the instructions on this page USB Driver for Windows but Windows never prompted with the "Found new hardware..." message.
I'm running Vista x64 SP2 and I can see the amd64 folder under ~\Android SDK\tools\usb_driver.
The Manage Devices applet shows no listing for "ADB Interface" so it certainly appears that it is not there. I tried a scan for hardware changes -- nada. And running "adb devices" comes back empty (as expected).
How do I install the ADB Interface?