Your keyboard files are typically located under the keyboards directory inside your Keyboard Assistant installation.
Common locations include C:\KeyboardAssistant\Keyboards or
C:\Program Files\KeyboardAssistant\Keyboards.
On Windows Vista/7 they may be under
C:\Users\<your_account>\AppData\Local\VirtualStore\Program Files\KeyboardAssistant\Keyboards.
Use the Help → Your keyboard folder is here option in Keyboard Assistant to locate them.