In this article we will explain how to upgrade your iPhone 4, iPhone 3GS to iOS 5.1 without upgrading your baseband on Windows. This will allow you to unlock your iPhone since you would be on a supported baseband.
Create a folder named Pwnage on your Desktop. Now download the latest version of RedSn0w from here to the Pwnage folder.
Step Two
Download iOS 5.1 firmware for your device from here into the Pwnage folder.
Step Three
Extract the RedSn0w archive file. Now run the RedSn0w executable as Administrator.
Step Four
From the Main menu, click on Extras.
Step Five
Now from the Extras menu, click on “Custom IPSW”.
Step Six
Now you would have to select the iOS firmware. Select iOS 5.1 firmware that you downloaded to the Pwnage folder and click Open.
Step Seven
Now RedSn0w will create a custom IPSW file for you.
Step Eight
Once the files has been created you would receive a prompt.. Click the OK button.
Step Nine
Now from the Extras Menu, Click Pwned DFU.
Step Ten
RedSn0w will now show you a menu, which would ask you to connect your device to the computer via USB and power it off. Once done, click the Next button to continue.
Step Eleven
Now you would be asked to hold down the Power button for 3 seconds. Do so.
Step Twelve
Now without releasing the Power button, hold down the Home button for 10 seconds.
Step Thirteen
Now release the Power button BUT KEEP holding the Home button until your device is in DFU mode.
Step Fourteen
RedSn0w will now exploit your device with LimeRa1n.
Step Fifteen
Once the exploit is done, your device will be in Pwned DFU mode.
Step Sixteen
Now launch iTunes. You would have to do so by clicking its icon on the dock.
Step Seventeen
From within iTunes, select your device from the list on the left and then hold the Shift key and click Restore.
Step Eighteen
Select the “NO_BB…” custom IPSW from the Pwnage folder and click Open.
Step Nineteen
Once the process is complete, your iPhone will be upgraded to iOS 5.1 without having the baseband updated.
via iClarified.
