Jailbreak tool GreenPois0n RC5 for iPhone 4, iPhone 3Gs, iPod touch and iPad on iOS 4.2.1 is now available to download for Windows users. GreenPois0n Rc5 supports untethered iOS 4.2.1 jailbreak without iOS 4.2b3 SHSH blobs on Cydia server. Jailbreaking your iDevice allow third party applications installation which are restricted on Apple App Store. We have a step by step tutorial and also a Video guide on how to jailbreak iOS 4.2.1 using GreenPois0n Rc5 for Windows.
iPhone 4 users! if you are on an older iOS version than iOS 4.2.1 with Carrier Unlocked, Follow this guide on how to preserve unlock and upgrade to iOS 4.2.1 (only for iPhone 4 users)
How to Jailbreak iOS 4.2.1 with GreenPois0n RC5
Warning: Do not upgrade to iOS 4.2.1 if you relay on an unlock. Ultrasn0w does not support the latest baseband yet.
Save the zip file on your desktop.
Extract by double click the downloaded gp_win_rc5_b2.zip file then drag the greenpois0n.exe file to the desktop. Double greenpois0n.exe to launch the application.
Power off and connect your iPhone, iPod touch or iPad with the PC. Now Click the large Prepare to Jailbreak (DFU) button
GreenPois0n will instruct you to put your device into DFU mode.
Press and hold the sleep button (the power on button) for 2 seconds.
Continue holding Sleep button and also Press and hold Home for 10 seconds.
Release Sleep button but continue holding Home for 15 seconds.
Now your device is in DFU mode. Click the Jailbreak button.
Greenpois0n will now jailbreak your device
Click the Quit button once the Jailbreaking is completed.
You’ll notice some verbose mode text scrolling on your device.
After restart you’ll notice a new Loader application on your Springboard. Touch its icon and launch it.
Touch on Cydia then press the large Install Cydia button that appears.
Once Cydia has installed successfully you can remove Loader by pressing the Options button then the large red Remove Loader.app button.
Restart your device then run Cydia. Let it do all the necessary updates.
Congratulations, you have a jailbroken iOS 4.2.1 device.
If you faced any problems, you can follow the video guide by DinoD7 below.