THIS JAILBREAKING METHOD WILL NOT UPDATE YOUR MODEM BASEBAND, WHICH ALLOWED YOU TO INSTALL ULTRASNOW TO UNLOCK YOUR IPHONE FOR OTHER CARRIERS.

Prerequisite:

*This custom firmware is for iPhone 3GS with old bootrom only

*Your iPhone must be previously jailbroken with any method except Spirit method, in order to jailbreak with this custom firmware

*Activation required AT&T active or non-active SIM card

*You must have internet connection during this entire process

Instruction:

1. Back up your iPhone with iTunes

2. When your iPhone is in operating mode, hold down Shift key on your keyboard and then click Restore button in iTunes and locate the file "iPhone 3GS Custom Firmware 4.2.1.ipsw" that came with this firmware, and ready to restore.

3. Once restore is done, the iPhone will activate

4. If you open Cydia then it will not open because you will need to update Cydia by doing step 5 and step 6 below:

5. SSH into your iPhone and copy the Cydia folder that came with this firmware into the iPhone directory given below:

/ private / var / root / Media

6. Reboot your iPhone

7. After reboot, now open Cydia has been updated, and you can open Cydia and perform all necessary updates as usual

8. Now you can restore your iPhone from backup by right click on iphone and click on restore from baackup and you're done