Sn0wbreeze 2.2.1 brings one stop solution for all your jailbreaking needs. Whether you wish to preserve your Baseband (for unlocking) or just jailbreak iOS 4.2.1 untethered, it does it all on your Windows.
How to Jailbreak iOS 4.2.1 Untethered + Preserve Baseband for Unlock
Download iOS 4.2.1 (Official from Apple)
1. Launch sn0wbreeze, we are now ready to create a custom firmware.
2. Browse the firmware file, and let it identify the firmware. When done hit Next and use “Expert mode”.
3. Feel free to chose any options you wish to have for modifications.
4. If you are on an unofficial carrier, Make sure you check “activate iPhone [Hacktivate]’ and Hit create button. Depending on your computer’s speed, it would create the file within minutes and place in the same directory as original firmware.
5. Next, Put iPhone to DFU mode as per instructions on screen.
6. Open iTunes SHIFT+ restore (on windows) & ALT + restore (on Mac os) and locate the firmware sn0wbreeze created.
Note: If you get errors use iREB to fix 16xx errors.
That’s it, enjoy your Unlocked, Jailbroken iOS 4.2.1 untethered iPhone/iPod Touch/iPad.