With iH8sn0w’s sn0wbreeze 2.2, you can jailbreak and unlock iOS 4.2.1 on Windows. Benefitting from Sn0wbreeze baseband preservation mode, you can create a custom IPSW that will allow you to upgrade to iOS 4.2.1 without updating your baseband. Here is the guide:
Jailbreak & Unlock 4.2.1 iOS with Sn0wbreeze 2.2
Before you Begin:
- Download sn0wbreeze 2.2.1 – Sn0wbreeze 2.2
- Download iOS 4.2.1 firmware
- Backup your data
Step 1: Launch Sn0wbreeze.exe, once you’re on welcome screen, click on “Browse” button

Step 2: Specify the location of iOS 4.2.1 IPSW and click ok. Sn0wbreeze will not identify IPSW and will display following screen when complete, Click on Next.

Step 3: In next step, you’ll get following options to choose from:
- Baseband Preservation Mode – Choose this if you rely on carrier unlock and want to unlock iOS 4.2.1
- Simple Mode – Recommended for basic users who just want untethered 4.2.1 jailbreak
- Expert Mode – Recommended for advanced users
Choose the one that suits you and then click on “Next” button.

Since most of sn0wbreeze users, we assume, will be those who want to preserve their baseband, we’ll be going ahead with sn0wbreeze baseband preservation mode.
Step 4: That’s all from your end. You can either sit back and watch sn0wbreeze jailbreak process or can play PacMan in the meantime.

You can find custom iOS 4.2.1 IPSW on your desktop. Load this custom IPSW to your iPhone (see how to).
Unlock iPhone 4, 3GS 4.2.1 iOS
Once your iPhone has been jailbroken, you can unlock it with ultrasn0w 1.0 by following the steps given below:
Step 1: Run Cydia from SpringBoard.
Step 2: Tap on “Edit”, then hit “Add”, a prompt should appear asking “Enter Cydia/APT URL”.
Step 3: Enter http://repo666.ultrasn0w.com/ and hit “Add Source”, then tap on “Return to Cydia”.
Step 4: Once the process completes, search for ultrasn0w 0.93 in Cydia and install it.
Step 5: After installation, reboot your iPhone.
All done!










Proofs are yet to come though and we will keep you updated. Stay tuned. Update 1: Here is the image of unlocked iPhone 4 posted by planetbeing:
