JailBreak your iPhone 4 iOS 4.1 using limera1n by GeoHot
This is a step by step guide, that will show you how to use limeRa1n to jailbreak your iPhone iOS 4.1.
LimeRa1n can jailbreak a various amount of iDevices:
iPod Touch 3G
Jailbreaking can void your warranty so use at your own risk.
I used a PC OS windows 7 to JailBreak my iPhone4
Download limera1n @ http://www.limera1n.com/
available for PC and MAC.
Connect your iPhone via USB and launch LimeRa1n then click Make it Ra1n.
Follow the prompted onscreen instructions and do exactly what it tells you:
Hold the Home and Power button together.
Release the Power button.
LimeRa1n now enter your iPhone into DFU mode while it proceeds to JailBreak your iPhone
Your iPhone is almost jailbroken and you should see the following messages.
Your iPhone will then display the Apple icon then power off, then you may have to turn your iPhone back on manually. The limera1n Logo will then appear as full screen display, then it may turn itself off again and you may have to manually turn it on (I tested this a few times with different results).
Open the spring board on your iPhone and open limera1n. It will either be a white box or it will have the specific limera1n logo. If you dont see the LimeRa1n icon on your iPhone, simply reboot it, then launch LimeRa1n on your iPhone and select Cydia to install.
Once Cydia is installed, you can delete the limera1n Application from your spring board.
ENJOY YOUR JAILBROKEN iPhone!