Original iPhones (metal back, silver color, referred to as 2G iPhone) are blessed with a fully unlockable baseband 04.05.04_G. It entitles the iPhone 2G to be easily hackable. So lets get the ball rolling and get to the latest 3.1.3 firmware with a full unlock, jailbreak and activation in place!
Step by Step :
Download redsn0w 0.9.3 from downloads section and extract them to your Desktop [Both Mac and Windows versions of redsn0w are available there]
Connect your iPhone 2G to your PC/Mac and launch iTunes [Update iTunes to the latest version]
Update to 3.1.3 firmware directly from iTunes itself [Just click the update button in iTunes]
Meanwhile, download 3.1.2 Stock iPhone firmware and save it on the Desktop [Make sure it is .ipsw extension and not .zip]
Once the update is done, launch redsn0w 0.9.3 and click on browse button and browse to the 3.1.2 firmware that you just downloaded [Saved on Desktop] and click Next as shown. Follow the screenshots and proceed accordingly [Make sure Unlock and Cydia are checked]
Download the bootloader files for iPhone 2G. Extract the downloaded files 39.bin and 46.bin to the desktop.
When you are prompted for the bootloader files 39.bin and 46.bin in redsn0w , browse to the respective files saved on the desktop and click Next.
Now make sure your iPhone is connected to your PC/Mac and turn it off [Hold the power and slide to power off] and click Next.
Now follow the on screen instructions carefully, it is ok to miss those on the first try. Click back and try again [The 3 steps should as prompted should be done in the time shown on redsn0w].
Now let redsn0w do its thing! You will see some images on the iPhone which means it is jailbreaking, unlocking and activating your iPhone 2G! Wait till you see the homescreen, in other words leave the iPhone alone for few minutes.
Enjoy your jailbroken, Unlocked iPhone!