Finally the Windows users can now enjoy the untethered jailbreaking for your iPhone, iPod touch or iPad. As you may already know Greenpois0n for
Windows has been released.
If you haven’t heard of Greenpois0n, it is the first stable jailbreak tool that supports untethered jailbreak on all devices running iOS 4.2.1. Developed by the Chronic Dev team, the tool doesn’t require you to have the SHSH blobs. You can simply jailbreak your device running iOS 4.2.1 out of the box.
I have tried to jailbreak my iPhone 4 using Greenpois0n. Despite there are a few hiccups, overall speaking, the jailbreak process is quite smooth. Here I come up a step-by-step jailbreak guide to walk you through the process using Greenpois0n. If you’re using iPhone 3GS or iPhone 4 and would like to jailbreak your device on iOS 4.2.1, you can simply follow the procedures and achieve the jailbreaking.
Before we dive into the jailbreak process, please read through the notes very carefully:
■ This guide is for Windows user. If you’re using Mac, please
check out the untethered jailbreak guide for Mac users.
■ Greenpois0n is a jailbreak solution that allows you to open up your device to install 3rd-party applications. It’s not a software-unlock solution. So if you are currently relying on Ultrasn0w to unlock your iPhone, please DO NOT upgrade your iPhone to iOS 4.2.1 directly. Otherwise you’ll lose the unlock and your iPhone will not be able to make call.
■ Greenpois0n does not come with hacktivation. That means you have to activate your iPhone before using the jailbreak tool.
■ Greenpois0n works only on iOS 4.1 and 4.2.1. However this guide is written based on the jailbreaking of iOS 4.2.1. We have not tested it on iOS 4.1.
■ Make sure you’re using iTunes 10.1 or up.
■ If you have used Redsn0w to jailbreak (untethered) your iPhone, I suggest you to restore it to iOS 4.2.1 via iTunes before using Greenpois0n.
Preparation for the Jailbreak
1. Download Greenpois0n RC5_2 from
greenpois0n.com or
mirror site.
Note: I suggest you to download the tool from the mirror site. The official site is extremely busy and not very stable for now.
2. Extract the greenpois0n-win_rc5_2.zip and you’ll have the “Greenpois0n” application.
Kick-off the Jailbreak Process
3. Connect your iPhone to computer via USB cable and power it off.
4. Launch the Greenpois0n application.
5. Click the “Prepare to Jailbreak (DFU)” button to kick off the jailbreak process. You can simply follow the on-screen instructions to put your iPhone into DFU mode. Keep holding the home button till the end of the jailbreak process.


Note: If you fail for the first time, power off your iPhone and goes through the process again. It won’t hurt.
6. As you successfully put the device into DFU mode, Greenpois0n will automatically jailbreak your device. On your iPhone, you’ll see the verbal messages in command mode. That’s normal. Just wait until Greenpois0n tells you the process completes.
Installing Cydia
7. After jailbreaking, your iPhone will be automatically booted up. You should find a new icon called “Loader”. Simply tap on the icon and launch the app.

8. Once launched, tap on the “Cydia” button to install cydia. This will initiate the download process. Just wait for it to complete and you’ll have cydia installed on your iPhone.
Note: If you found the cydia button missing after launching Loader app, just quit it and try again.
9. After successfully installing cydia, you can tap the “Option” button and remove the Loader app.