Chronic Dev Team has already released Windows version of GreenPois0n RC5 iOS 4.2.1 untethered jailbreak for iPhone, iPad and iPod touch. It allows users to perform an untethered jailbreak on iOS 4.2.1 devices. This release works to jailbreak all iPhone, iPod touch, iPad models. Here is the step by step guide for Windows users to apply untethered jailbreak on iOS 4.2.1 devices while using Greenpoison RC5. Greenpois0n Windows version jailbreaks all idevices except Apple TV2, which will supported in the next update.