How to Jailbreak Your iPhone 3GS, iPhone 4 Using Greenpois0n (Windows)
 

Step One
Open your web browser of choice and navigate to http://www.greenpois0n.com. Click the Windows link at the bottom of the screen.
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Step Two
When prompted save the download to your desktop
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Step Three
Double click the downloaded gp_win_rc5_b2.zip file then drag the greenpois0n.exe file to the desktop. Double greenpois0n.exe from the desktop to launch the application
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Step Four
Power off your iPhone then click the large Prepare to Jailbreak (DFU) button
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Step Five
You will now be instructed on how to place your iPhone into DFU mode. You can get help with this here.
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You will be asked to press and hold the sleep button for 2 seconds.
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Continue holding sleep; press and hold home for 10 seconds.
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Release sleep button; continue holding home for 15 seconds.
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Step Six
Once your iPhone is successfully in DFU mode you may click the Jailbreak button.
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Step Seven
Greenpois0n will now jailbreak your device
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Step Eight
Click the Quit button once the software application has completed.
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You'll notice some verbose mode text scrolling on your device.

Step Nine
After the iPhone restarts you'll notice a new Loader application on your Springboard. Press to launch it.
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Step Ten
Press to select Cydia then press the large Install Cydia button that appears.
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Step Eleven
Once Cydia has installed successfully you can remove Loader by pressing the Options button then the large red Remove Loader.app button.
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Step Twelve
Restart your iPhone then run Cydia. Let it do all the necessary updates then follow our Unlock tutorial if possible for your device.
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