The 1G had started to die though, with error messages constantly popping up.  Each time the message would pop up, the screen would turn on, so the battery could only last a few hours.

She bought a used 8 GB 3G iPhone locked to Rogers to replace it, however the previous owner had updated it to official Apple iPhone firmware 3.1.3 which did several things to make unlocking it to other cellphone networks impossible.

With iPhones, there are two distinct hacks: jailbreaking means that you can run home-made software on your iPhone without needing to go through Apple’s official App Store.  Unlocking, like with any other cellphone, means that you’re not restricted to any one particular cellphone carrier.

In addition to the main iPhone operating system, (now known as “iOS” as it’s shared with the iPad), there is separate firmware that controls the modem in the phone: the part that actually connects with the cell network.  This firmware is known as the baseband.  Finally there’s a bootloader as well, which may be governed by the hardware iteration rather than software, but I’m not sure.  The jailbreak used to be mostly dependent on the operating system, the unlock used to be mostly dependent on the baseband version.  The bootloader determined whether or not you could restore your iPhone to older versions of baseband which could then be unlocked.

The sum total though was that with old hacks, it was impossible to unlock my girlfriend’s 3G iPhone to work with her cell provider.

Once iOS 4.0 was released however (June 21, 2010), the brilliant hackers that figure out how to jailbreak and unlock these things published exploits they had been withholding.  They’d been waiting for iOS 4.0 to come out to get more mileage and not waste them on an otherwise minor firmware update.  These current exploits work with ALL iPhones from 3G onwards, all basebands, and all bootloaders.

To unlock your 3G:

1. Sync your phone with iTunes.  Make sure it creates a backup.  If it doesn’t (from ericajoy, found with Google):
   • Open iTunes
   • Go to Preferences
   • Choose the syncing option
   • Remove the iPhone backup
   • Press OK and exit Preferences
   • Sync your iPhone
2. Update your 3G to the proper full iOS 4.0 with iTunes. It should be prompting you to whenever you connect your phone to your computer with iTunes open.
3. Download and run Redsn0w from the Dev-Team Blog.  The earliest version that works with iOS 4.0 is 0.9.5b5-4.  (Click the Windows link on the post I linked.)
4. It will ask you to point it to the IPSW file of your CURRENT FIRMWARE (which will be 4.0 now if you followed step 1.)  The file is called iPhone1,2_4.0_8A293_Restore.ipsw.
   • In Win7 it will be found in C:\Users\<YOUR USER NAME>\AppData\Roaming\Apple Computer\iTunes\iPhone Software Updates
   • In WinXP it would be found in C:\Documents and Settings\<YOUR USER NAME>\Application Data\Apple Computer\iTunes\iPhone Software Updates
   • Alternatively, you can just download it separately from a site such as this one.  (Look for the iOS 4 section at the bottom of the page and click the iPhone 3G link.)
5. Redsn0w will take some time to process the IPSW file, then it will prompt you for some options after you hit ‘next.’
   • The option you must select is “Install Cydia.”  Cydia is the programme that installs all the non-Apple approved iPhone applications, and will be required to actually unlock the phone.
   • On the 3G I recommend you also enable the “homescreen wallpaper” and “battery percentage.” The 3G isn’t really fast enough to do multitasking well, but it’s up to you.  Leave everything else unchecked.
   • 
6. Your iPhone should be connected to the PC already.  Turn it off by holding the power button on top, and swiping across the screen when asked to.  Hit ‘next’ and follow the rest of the on-screen instructions.  Redsn0w is going to ask you hold the power button for a few seconds, then hold the power & home button for 10 seconds, and then let go of the power button while still holding the home button for 30 seconds.  You can let go of home once the screen changes and things start happening on your phone.  If gives you another chance to do it over if you screw up.
7. The rest of this is automated.  It can take a while to finish.  Redsn0w on your PC will soon say it’s done, that the rest takes place on your iPhone.  You can close redsn0w at this point.  I believe it took about 10 minutes for the iPhone to finish it’s business.  You now have a jailbroken iPhone 3G.
8. To finish the process and unlock the phone, run the Cydia app on your homescreen.  It will take some time to update itself.  (Roughly five minutes.)
9. Click on the search tab, and search for “ultrasn0w” (the “o” is a zero, like in redsn0w).
10. Install it, and select reboot once it asks you to.  Your iPhone 3G is now unlocked.

From now on, do not install any new official Apple firmware until you’ve absolutely confirmed that you can jailbreak and unlock it.