When I first connected the Xoom to the PC with the USB cable, at first it looked as things would go fine. My Windows Vista PC saw a new device had been connected, and began installing a driver --- or so it appeared. But after taking far too long to install it, Windows told me the drivers hadn't been installed properly. I tried restarting my PC and trying again. That didn't work, either.
Next, I figured that if could find the actual drivers, I'd be able to install them manually. But after a half hour of searching the Motorola site, the Verizon site, and the Web, the drivers couldn't be found.
Instead, I found Motorola's MotoHelper application, which installs drivers for you. I'm not a big fan of these kinds of tools, and prefer installing drivers myself when I can. But I had no choice.
That didn't solve the problem, either. I ran it several times, told it to update my drivers, and each time I got the same result --- the same error message I had received from Windows the first time around.
Finally, I turned to a live chat with Motorola technical support, and after a few minutes they solved the problem. I had to first enable USB debugging on my Xoom, then connect the Xoom to my PC with a USB cable.
To enable USB debugging, go to Settings, then tap Applications --> Development, and check the box next to USB debugging. (See the screen show, below.)
I unplugged my Xoom from my PC, enabled USB debugging, plugged it back in, and with a few minutes, the driver installed, and all is right with the world. Afterwards, I remembered that I had the same issue with my Droid X. If anyone out there knows why you need to enable USB debugging, let me know in the comments, below.