Thanks for the tip. However, installing the LG tool above didn't work for me. Crashed during install. Here are the full instructions from start to finish on how to get USB tethering working on Windows 7 on Sprint LG Optimus S using another method. You will need a 3G-connected Android phone, an internet-connected Windows PC, and the USB cable to connect the phone to the PC.
1) Go to this thread on AndroidCentral :
[HOW TO] Install USB drivers for the LG Optimus One - Android Forums
2) Scroll down to post #8, where the actual driver file package is posted. Register for a user profile on androidcentral if you don't already have one.
3) Click the 3rd link, where the driver files are hosted on another site.
4) Download only the top file,
LGAndroidDriver_WHQL_ML_Ver_1.0_All_Win7
5) Install it on your Windows PC (I only tried Win7 so far)
6) On your Optimus S, enable USB Debugging, through the Settings->Applications->Development menu
7) Plug your Android into your PC through USB. Lots of drivers should be installing now. Wait until they're all done installing.
8) Unplug your Android from the PC.
9) Go to Android Market on your Optimus S, and install the free app PDANet. After install, it may ask you if you want to download more software for your PC Desktop client. Don't download that on the phone, instead choose "Already Installed".
10) On your PC, go to the PDANet page here :
PdaNet -- USB Tether/Bluetooth DUN for Android and click on Download for Windows, then install it.
11) During the install, it should warn you that you already have Android drivers installed. It will ask you if you want to reinstall more drivers anyway. I clicked No, don't reinstall any drivers.
12) After that, it will ask you to connect your Android to your PC. Do it, and connect through USB.
13) The PDANet install on Windows should now complete, and you will have a small PDANet icon in the lower right corner.
14) Now to use USB tethering, go to the app "PDANet" on your Optimus S, and run it. Click on "Enable USB Tether". Then go back to your PC, and click on the PDANet icon in the lower right corner, and select the top choice "Connect Internet".
Good luck.
- JoeSero