These are instructions on how to jailbreak your iPhone 3GS and iPhone 4 using Greenpois0n for Windows. Greenpois0n only supports iOS 4.1 firmware. Use Limera1n if you want to jailbreak iOS 4.0, iOS 4.0.1, iOS 4.0.2.
Remember: Do not update to iOS 4.1 if you need the unlock. Ultrasn0w does not support that baseband yet. The only exception is the iPhone 4. You can update to iOS 4.1 without upgrading your baseband by following this tutorial.
Open your web browser of choice and navigate to http://www.greenpois0n.com. Click the Windows link at the bottom of the screen.
You will now be instructed on how to place your iPhone into DFU mode. You can get help with this here.
You’ll notice some verbose mode text scrolling on your device.
Once Cydia has installed successfully you will be asked if you want to remove Loader from your device. Press the Remove button then press the Home button. Your device will now automatically reboot.
When your iPhone has restarted you can run Cydia. Let it do all the necessary updates then follow our Unlock tutorial if possible for your device.
***A big thanks goes everyone who made this jailbreak possible.
Download : Linux & Windows Version