"Tethering" is the process of linking two electronic devices together and sharing Internet capabilities. In regards to the iPhone, tethering refers more specifically to offering Internet to your computer from the iPhone's Wi-Fi or 3G connection. However, it is also possible to reverse the connection. For instance, if you have a LAN connection on your PC and no access to Wi-Fi or 3G, you can share the Internet from your computer with your iPhone with reverse tethering.
Connect your iPhone to your PC using a proprietary USB cord.
Access "Network Connection" and right-click on the "Wireless Area Network" icon. Select "Properties" and click the "Wireless Networks" tab.
Click the "Add" button to set-up a new wireless network. Type "Reverse Tether" into the cursor box labelled, "SSID."
Click the box next to "This Is a Computer-to-Computer (Ad-Hoc) Network" and then click the "OK" button.
Click the "Advanced" button and click the box next to "Computer-to-Computer (Ad Hoc) Networks Only." Select the "Close" button.
Click the "General" tab and then double-click the list item entitled "Internet Protocol (TCP/IP)." Set the IP address to 10.0.0.1 and the Subnet Mask to 255.0.0.0. Select the "OK" button.
Select the "Settings" button on your iPhone and access the "Wi-Fi" menu. Select "Other" and type "Reverse Tether" into the SSID box.
Press the blue arrow to the right of the new "Reverse Tether" connection to access advanced settings. Touch the "Static" button and type 10.0.0.2 into the box below. Enter 255.0.0.0 into the Subnet Mask box.
Touch the "Manual" button and type 10.0.0.1 into the "Server" box and 8080 into the "Port" box.
Access the "Wi-Fi Networks" screen once more and select "Reverse Tether." You may receive an error message, but your computer and iPhone will be tethered together.
Write down all Internet settings before attempting the procedure above. This record will be very helpful if you decide to return your settings to normal.