Yes I Can!

How to Unlock iPhone 3GS on iOS 4.1 with Ultrasn0w

Step 1: Unlocking requires that your phone is jailbroken on the latest firmware. Follow the complete guide to jailbreak your iPhone 3GS (old bootrom only) on iOS 4.1 using PwnageTool.

How to: Unlock iPhone 3GS (old bootrom) on iOS 4.1:
Step 2: Once you are done with the jailbreak, you can now unlock your iPhone on the older baseband using Ultrasn0w 1.1-1 from Cydia. To do this:

* Start “Cydia” on your iPhone.
* Touch on “Manage” tab on the bottom.
* Now touch on “Sources” as seen in the screenshot below:
LinkShare Referral Program

LinkShare Referral Program
Touch on “Edit” and then on “Add”. You will be prompted to enter a url source as seen in the screenshot below. Type “http://repo666.ultrasn0w.com” and touch on“Add Source” to add this repo if you haven’t already.

Cydia will now automatically update your sources by following a series of automated steps.

* After installation is completed. Search for “ultrasn0w 1.1-1” in Cydia and install this application. This app will automatically unlock your iPhone so that you can use it with any carrier.

Step 3: Now simply restart your iPhone and voila! you should now have a fully unlocked iPhone !