After a bit of hunting and pecking we gave Proxoid a try. From the home page:
Proxoid is a ProxyServer on Android. It allow users of not rooted phones to use their phone's internet access from a computer.
It seemed reasonable, but we couldn't get it to work; the driver installation never completed, and we couldn't get Windows XP to comprehend the phone that was connected via the USB cable.
So we gave PDANet a try. From the PDANet home page:
PdaNet does NOT require root access or hacking your phone's firmware in order to work. It is just a regular Android application that works on all Android phones as-is. Your phone can connect to the data service, WiFi, or even through VPN and PdaNet will share the connection with your computer.
The PDANet installer whirled and hummed, and it, too, was having trouble getting the right drivers installed.
HOWEVER, the PDANet installer gave us a clue:
Sometimes if USB debugging is checked but there is still no "Android ADB Inteface" listed when phone is attached or if there is a driver error, your system may need the official USB driver for some reason. If that is the case, install one of the following drivers on your computer first:
Driver for LG Android Phones
Once we got that special LG driver installed, the rest of the PDANet installation proceeded without complaint, and a few minutes later we were online, tethered via the phone!
Quite possibly, the installation of the LG driver would have enabled Proxoid to work, but since the PDANet software seemed to be working and diagnosed the problem well and clearly, we've decided to stick with that for now.
Smart phones are a fast-moving technology; I suspect that, in a year, we'll be setting up a new computer with a new smartphone, and we'll be amazed how much things have changed, and how easy they've become. Still, the PDANet installation process was overall pretty reasonable, so I'm suitably impressed.