This guide will teach you how to jailbreak AND unlock your iPhone 2G running 3.0 firmware using RedSn0w on Windows.
I strongly recommend you backup and restore your iPhone 2G to 3.0 firmware via iTunes BEFORE you begin this guide. By strongly recommend I mean restore to 3.0 firmware.
You will need RedSn0w 0.7.2 which you can download here along with the iPhone 2G 3.0 firmware file available for download here. You also need the 3.9 and 4.6 bootloader files. Download 3.9 here and 4.6 here.
Once you have downloaded everything, extract redsn0w-win_0.7.2.zip to a location on your computer. You should see redsn0w.exe. Run it.
Find your iPhone 2G 3.0 firmware file you downloaded earlier. Select it and click Open.
RedSn0w tells you that the ISPW is successfully identified. Click Next.
There will be a quick pop up.
Select your options to Install Cydia and Unlock. If you don't need to unlock your iPhone 2G you can de-secelct Unlock
If you are unlocking you need to located the 3.9 and 4.6 bootloader .bin files you downloaded earlier.
Now that you have told RedSn0w where the bootloader files are click Next.
At this point you should make sure your iPhone 2G is plugged into your computer AND turned off. Click Next.
RedSn0w gives you instructions. We are entering DFU mode now. First hold the power button for 3 seconds.
Keep holding the power button and start holding the home button for 10 seconds.
Release the power button but continue holding the home button for 30 seconds.
RedSn0w does its thing. Let it.
Finally RedSn0w has finished loading everything onto your phone. You will see a pretty screen on your phone as it is being Jailbroken and Unlcoked. Don't mess with your phone while all this is going on. After your phone restarts you are done!