#1: Download and install iTunes 10 from ih8sn0w.com/index.php/welcome.snow
#2: Download iOS 4.1 for your iDevice from geekword.net/ios-4.1-ipsw-download-links/
#3: Download and install snowbreeze 2.0.
#4: Launch Snowbreeze and activate Expert Mode.
#5: Snowbreeze 2.0 will asking for the iOS 4.1 IPSW single file. Guide it to the location/folder where the necessary file is set. The microcode will follow verified. Once done, click Next.
#6: iPod Touch users can jump this step. Now if you're on iPhone 3GS, make sure you hit General and check Use iBooty process. Also check Activate The iPhone if you're on unauthorised carrier
#7: Select Build IPSW. Snowbreeze will now create the custom .ipsw single file for your iDevice which will be jailbroken
#8: link your iDevice to iTunes and choose your iDevice from the left hand navigation pane in iTunes. Check Down the SHIFT key on your keyboard and hit the repair button.
#9: iTunes will move you for the iOS 4.1 IPSW file. Guide it to the location/folder where the needed file is located.