This instruction will explain how to perform iPhone 4 iOS 5.1 jailbreak with redsn0w on Windows. Firstly you need to know that it's kinda dangerous to update to iOS 5.1 if you're not on it yet. The thing is - you can lose your unlock if your iPhone isn't factory unlocked because by updating your iOS version iTunes will most probably upgrade your bb version. And, as you probably know, there's no unlock for some iPhone 4 basebands. So if you're not sure about it - better stay away from it. In this tutorial we will assume that you're already on iOS 5.1. It's always a good idea to save your SHSH blobs before jailbreaking. Despite the fact that iOS 5.1 jailbreak for iPhone 4 was released the day after iOS release, it's still tethered. You'll find the instructions how to boot tethered below.

How to Jailbreak  iPhone 4 iOS 5.1 with redsn0w Windows:

Step One: Create the folder on your desktop. Name it as you wish. Step Two: Download the latest version of redsn0w (you can do it here). Step Three: Unarchive redsn0w to the folder you've created on your desktop and run the program as administrator (right click on redsn0w.exe and select Run as administrator in the menu). Step Four: Click Jailbreak button. Step Five: Turn off your iPhone and plug it in your PC via USB cable. Step Six: Follow redsn0w's on-screen instructions to enter the DFU mode. Step Seven: Your device will be now exploited with limera1n and will reboot. Step Eight: Redsn0w will prepare the jailbreak data and jailbreak the device. Step Nine: Select only Install Cydia from the list and press Next button. Step Ten: Wait until the program uploads ramdisk and patches kernel. Step Eleven: You'll see the Done window after the jailbreaking process is completed. Now your iDevice is jailbroken tethered. You'll see Cydia icon on device's SpringBoard.

How to boot tethered after iPhone 4 jailbreak on iOS 5.1: Step One: Run redsn0w and connect you iPhone to PC. Step Two: Choose Extras in program's main menu. Step Three: Within Extras menu choose Just boot to boot tethered and wait. Your device will be in tethered state until some of the hackers (probably pod2g) releases untethered jailbreak for iOS 5.1 or iOS 6 which will probably be introduced at WWDC in June. Let's hope that we'll get iOS 6 untethered jailbreak right after initial iOS release. If you have any questions about this how-to please feel free to comment below. We'll answer your question asap.