This is a simple, clear and easy tutorial on how to both jailbreak and unlock the iPhone 2G on iOS 3.1.3 (the final firmware version for iPhone 2G). This tutorial is the same for both Windows and Mac.

Download Links

Redsn0w 0.9.4 -  Windows
Redsn0w 0.9.4 -  Mac
iOS 3.1.2 for iPhone 2G
iOS 3.1.3 for iPhone 2G
3.9 bootloader
4.6 bootloader

First of all, please make sure that your iPhone is currently on the iPhone 3.1.3 firmware.

Step 1:
Connect your device to the computer via your USB cable and launch the Redsn0w application you have just downloaded.

Step 2: Select the 3.1.2 (note, not 3.1.3, please select the iOS 3.1.2) firmware file that you downloaded for your device.

Step 3: Once the firmware file has been loaded click the next button to continue

Step 4: Redsn0w will now prepare the firmware file for patching

Step 5: At the next screen you will select all the options you want for your custom firmware. Please select 'Cydia' as well as 'Unlock'. You can also select custom boot logos if you wish. Verbose boot displays detailed information about your device during boot, this option is typically for advanced users.

Step 6: Next, select the bootloader files which you downloaded at the beginning of this tutorial.

Step 7: At this point turn your device off making sure it is still connected to your computer. After you hit next Redsn0w will walk you through getting your device into DFU mode. Basically you hold down the home button and the power button for 10 seconds, then you release the power button but continue holding the home button for another 10 seconds. At this point you will hear your computer beep when it detects a new device.

Step 8: At this point you will see redsn0w waiting for your device to reboot (Windows users please note that if you see “waiting for reboot” for longer than 20 seconds, try disconnecting your device from the cable while redsn0w is still running and then connect it back this is called ‘shaking’ the jailbreak process)

Step 9: Now Redsn0w will begin uploading the new RAM Disk and Kernel

Step 10: Alright, you made it! Once Redsn0w is done click the finish button. When your device is finished rebooting, a window will open on your iPhone which will install the bootloaders and unlock your device. Congratulations!