GreenPois0n RC6.1 to jailbreak all idevice iOS 4.2.1 untethered is now available for download. Chronic Dev-Team has released the GreenPois0n RC6.1 and bug fix for iBooks & WiFi, which provides untethered jailbreak for iOS 4.2.1 firmware.
Greenpois0n RC6.1 has been released for Mac OS X & Windows. Greenpois0n can jailbreak all iDevices including iPhone 4, 3GS, iPod Touch 4G, 3G, 2G and iPad, Apple TV 2G running iOS 4.2.1 firmware.
Download GreenPios0n RC6.1
Also You Can See This Video Tutorial For Jailbreak Your Apple Device