This is what I did - All of these instructions were done on an Windows-based PC, This is not my work - I found this info on the web.
You'll need a USB data cable, Motorola drivers, an original system image of the Xoom firmware - I got mine from this thread on here: http://forum.xda-developers.com/show....php?t=1049485
and part of the ADB SDK - I got this from here http://www.android.net/forum/downloa.../SDK_tools.zip
- extract this zip to the root of your C: drive so the folder looks like this: C:/SDK_tools
Once you have downloaded the correct system image for your device (I used Build H.6.2-24 for Retail Europe as I have a Xoom WiFi 604) extract all the files from the zip and copy them into the SDK_tools folder, make sure they are not in a sub-folder - they should be in the same directory as the fastboot files. The directory contents should look similar to this - don't worry if its not identical - as long as your img files are there together with adb and fastboot you should be OK:
Make sure you also have the Motorola windows drivers installed.
Once you've done this turn on your Xoom and enter fastboot (power on with power button plus vol+ then after 3 seconds press Vol- till you get fastboot on screen) as long as you see "Starting fastboot protocol support" on your Xoom screen it should work. Connect your Xoom to your PC via the USB cable. Open a command prompt on your PC and cd into the SDK_tools directory. Once in there type the following commands at the C:> prompt one at a time:
fastboot flash boot boot.img
fastboot flash system system.img
fastboot flash recovery recovery.img
fastboot flash userdata userdata.img
fastboot erase cache
fastboot oem lock
This should completely restore your Xoom to factory and lock the bootloader. This will allow official updates to download and should get you back to original.
This worked on my UK Xoom WiFi and allowed me to install official OTA updates from Motorola. The first time I ran the above I left my Xoom unlocked but was then unable to update OTA.
I hope the above is helpful. As I've said this is not my work and was gathered together from resources on the internet. It worked for me so hopefully will work for you too - good luck and let me know how you get on.