To get out of the boundaries set by Apple Company for your iPhone 2G you need to jailbreak it. For this act follow the steps that are described below. It is made easy and simple to get the liberty for your iPhone 2G.
1ST Step
You need to create a new folder with the name ‘pwnage’ on the desktop after that you have to download files listed below and place them in the newly created folder ‘pwnage’.
RedSn0w
-BL 3.9
-BL 4.6
-3.1.3 (2G): iPhone1,1_3.1.3_7E18_Restore.ipsw

Take RedSn0w app and put it in Pwnage folder.

2^ND Step

Now you are directed to connect your iPhone2G to the computer and launch iTunes.

Select iPhone2G from the devices. Then press shift and click Restore button. It is preferred as it would not create any unwanted space on iPhone2G.

Get to the Pwnage folder created on the desktop to select firmware ipsw. Now you can click open to carry on with the process.

3^RD Step

When your iPhone2G has been updated to the firmware by iTunes you may launch RedSn0w.exe from the Pwnage folder to the desktop.

4^TH Step

When RedSn0w get opens click on the browse.

5^TH Step

Now you are directed to select the firmware ipsw you put in pwnage folder and open it.

6^TH Step

After the verification of firmware gets completed click on the next button.

7^Th Step

This window offers several Jailbreak options you may select that you like. If the device is already pwned check already pwned option and continue.

It is strongly recommended to check Cydia and unlock options. Then click the next button to continue

8^TH Step

Set the location for bootloader files.

Click on browse and select 3.9 bootloader file from pwnage folder present on the desktop.

Now click on the browse to select 4.6 bootloader file from the same Pwnage folder.

Now click on the next button.

9^TH Step

Plug in iphone2G to the computer and you must keep it off. Then click on next.

10^Th Step

Now RedSn0w would assist you to get into DFU mode.

Keep pressed both Home and Power button for 10seconds.

Release the Power button but keep Home button pressed so that RedSn0w detect iPhone2G.

11^TH Step

Wait your iPhone2G will reboot now.

12^TH Step

RedSn0w now begins to upload new RAM Disk and Kernel.

13^TH Step

On the Completion you would be notified that RedSn0w is done so you click on the finish button. After the reboot of iPhone it will run BootNeuter to unlock and jailbreak and show Cydia on the springboard.

*Another great work done by iPhone Dev-Team for iPhone Users.