A two-pronged approach is required here. First, you must identify what different features of the application's base framework are being utilized. The differentiation could be, for example, on the basis of heavy dependency on certain data structures, interprocess communication being performed, or the activity of report generation. This is the easier part.
However, as the second step, I recommend that you become more confident and pick up pieces that use a type of technology that is different from what is being used currently. For example, there could be a piece of code relying upon simple data structures or XML-based persistence. Identify such baggage in the system and mark it for the transition. A lot of prudence is required in ...
