There are many leaked pre-release downloads of the newest iPhone OS available.
If you’re not a developer, let me just say you should NEVER attempt to use a beta device operating system.
However, if you did get your hands on one of these downloads and upgraded unwittingly, you may encounter issues.
What if you want to downgrade back to OS 2.2.1? Nope. iTunes will just point and laugh – IF you go about it the usual way.
Even if you try putting your device in ‘restore’ mode (with “Connect to iTunes screen”) iTunes will tell you the device cannot be restored.
At this point, you’re probably thinking, “Great…I have an expensive paperweight…”
Don’t worry. You simply need to fool the device and iTunes into letting you restore your 2.2.1 firmware.
To do this, you need to get your device into DFU (Device Firmware Update) mode.
NOTE: This procedure may or may not always work when dealing with the final version of 3.0 / 3.1.1. It is intended for those downgrading from the 3.0 BETA.
Open iTunes and connect the device to your computer.
Press and hold the Home button (on front of device) and the Sleep/Wake button (on top of device) at the same time.
After 10 seconds (exactly) release the Sleep/Wake button. Keep holding the Home button for a few more seconds. Release it just before you think the Apple logo will appear on your screen. The screen will be black – as though the device is off. Don’t worry. This is normal.
Wait a few seconds. iTunes should tell you it has detected an iPhone / iPod in recovery mode (even though it’s really DFU mode). You will now be able to restore your device with a 2.2.1 firmware file. To manually pick a file to use Shift-Click (Windows) or Option-Click (Mac) on the “Restore” button in iTunes. A browser window should pop up to let you choose a file.
Once you have restored your device using OS 2.2.1, you will be able to set it up as a new device or restore from an existing backup.
Here some preview pics that i have done...
Downgrade to iPod2_2.2.1_5H11a_Restore
Upgrading to 3.0 iPod2,1_3.0_7A341_Restore
so we can Jailbreak and back again the Cydia
Here we go Finish and Done and we can Jailbreak using Redsnow 8.0
Remind Feedback Ipod2 3.1.1 cannot Jailbreak i observe some few days ago
So i share my simple referral to all us......
Update Here http://gsmtools.biz/forum/showthread...6061#post36061