Note: *this method involves rooting and technically voids your warranty (and carries a slight risk which neither I nor Phandroid/Android Forums or anyone else on the forums can be held accountable).
Here is how I unistalled ICS and went back to Gingerbread.
Unlock the bootloader and install a stock recovery img:
and download the android-sdk, place it in the root of your computers c:
drive (not in programs)
Open the SDK Manager.exe - leave the Android SDK Tools unchecked (should already be installed) and check Android SDK Platform Tools. After you are done updating, close the Android SDK Manager.
Download recovery-clockwork-22.214.171.124-crespo.img from here
Place the .img file in your C:\Android\android-sdk\platform-tools folder.
1.Shutdown the phone
2.Hold down volume up + power
3.Now you are in the standard recovery mode
4. Plug in your phone via USB
5. On your computer press start ----> run and type cmd to open a command window.
6. Type cd /
7. Type cd Android/android-sdk/Platform-tools
Assuming you have SDK installed with fastboot now on terminal/windows or Windows cmd depending on OS type "fastboot devices" to check your device can be seen via USB
5.Assuming you device is seen via fastboot devices, now type fastboot oem unlock
6.Accept ... and new bootloader is unlocked. Your phone should now ask you if you want to unlock the bootloader.
After your bootloader is unlocked, go back to the cmd prompt on your computer and type: fastboot flash recovery recovery-clockwork-126.96.36.199-crespo.img
On your phone scroll down to recovery and select it (using the volume and power keys), it should reboot into ClockworkMod Recovery v188.8.131.52
Go back to your computer and download the stock Gingerbread from here
Open the file with winzip, and click the first file called: Stock-2.3.2-GRH78C-Nandroid to open the folder called: clockworkmod
Extract that folder (clockworkmod) to your desktop
Return to your phone and scroll to mounts and storage, then to mount USB storage.
Open your computer and navigate to your android folder, mine is Removable Disk H:
Copy the clockworkmod folder to your sd card
on your phone click unmount, then click +++++Go Back+++++
Then click backup and restore
Then select file: 2011-02-23.07.34.597/
---Your phone should then install good old gingerbread! -----