The procedure of unlocking the firmware 3.0 has already been discussed here but for the sake of simplicity, we will define it here too.

Follow the following steps in exact order to get your iPhone 2G unlocked:

1. Download the PwnageTool 3.0 (Direct | Torrent)
2. Make sure to download bl39.bin and bl46.bin
3. Install the iPhone firmare for iPhone 2G from here.
4. Run the PwnageTool and follow the steps on the software.
5. Once the custom firmware is made, enter DFU mode and restore the firmware.

Note: To enter DFU mode, watch this easy tutorial. Also while clicking the restore button, hold ‘Shift’ in Windows and ‘Option’ in Mac to browse to the custom firmware file.

Unfortunately the PwnageTool does not work for Windows users so just make use of the following custom and unlocked firmware 3.0 files for iPhone 2G.

1. Download the Custom/Unlocked firmware 3.0 files above.
2. Combine the files with HJSplit (for Windows) and Split&Concact (for Mac).
3. Now you will have on file named iPhone1,1_3.0_7A341_Custom_Restore.ipsw
4. Simply boot into DFU mode and restore the Custom/Unlocked firmware 3.0.

If you follow each and every step mentioned here carefully, then you should have an Unlocked iPhone 2G running on firmware 3.0. Good Luck!