first you need to install the fix (cab) for tethering with WM6.1
here it is:
Internet Sharing FIX.zip
after you install this cab perform a soft-reset of your phone (just restart it)
After you phone completely finishes booting up follow these steps:
1)Open Up your browser on your phone and wait for it to display a webpage.
2)Minimize the browser
3)Open up Internet Sharing in your programs folder on your phone
4) Choose USB under PC Connection
5)Hit connect (bottom left)
6)Turn OFF the Wi-Fi on your PC
7)Connect your USB cable to your phone & PC
You should momentarily see two little computers connecting next to the clock in your taskbar on your PC
Open up your browser on your PC and BAM!