How to Tether
1. Every other guide out there will ask you to use the PDANet App as a Wi-Fi Router – don’t do this! The connection will be horrible and unreliable. It’s far, far easier to just use PDANet Desktop, which works on every version of Windows from XP to 7.
2. First, start off by jailbreaking your phone, there is an amazing guide here
3. Once the jailbreak is complete, download the PDANet Desktop Application to your PC and the PDANet App to your iPhone
4. Install PDANet Desktop on your PC, the process should be very simple
5. Go into the PDANet App on your iPhone and switch over to USB mode in the settings.
6. On the iPhone, disconnect from any Wi-Fi networks to use your 3G connection.
7. Open the PDANet app on your phone and leave it open
8. Go into the Taskbar application on your PC for PDANet and Right Click, then select “Connect"
9. A Prompt will appear telling you what’s happening and whether or not the connection went through
10. You’ll know the connection is good once you have the PDANet App on your iPhone reading back to you the number of bytes sent and received
11. As soon as everything is set up, open your browser on the PC and navigate to www.google.com
12. If Google manages to connect, you’re good to go