Need to return a Motorola Bravo to factory standard

[Dlinn]

I have acquired a Motorola Bravo ATT. Some one has changed the operating system to something called ICS. Most things function OK but not as good as the one I have that is factory standard. I am an experienced Land Mobile radio technician but am not much on cell phones.
Can some one direct me to the necessary files and give me a very brief explanation on how to convert it back.

Thanks and have a nice day.