Chiphazard presents a detailed step-by-step tutorial on how to jailbreak Apple TV 2 iOS 4.2.2 untethered using Sn0wbreeze 2.7.3 for Windows.
The tutorial begins with the downloads from: iOS 4.22 for Apple TV 2G and Snowbreeze 2.7.3 (Windows). Following the next few steps as mentioned in the tutorial you’ll be able to  jailbreak Apple TV 2 iOS 4.2.2 as untethered.
In the next step you simply need to connect your Apple TV 2G to your TV set and you will notice nitoTV in the main menu. It is advised that you go in Settings and update nitoTV.
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