Creating interface with the software without API-Possibilities
Ask the company that makes the software if they have an SDK or documentation on their API.  Even if they have one, if you already don't like the application, this may not be much use to you.
If the main purpose of the application is to report on the contents of a database, there are plenty of libraries in python for reading/writing to databases.  SQLAlchemy/Storm and PyQt could probably do what you want.
I have one proprietary software my office uses for database access and reporting which nobody likes in my office. I am thinking of building a python/Java application with a simple interface which does the task of communicating with the propriety software. My problem is: Since the software is proprietary, there is no known API of any sort I am aware of such that I can interface. Is there a way around to get through this or is it mandatory to have API to access the software? I am doing this in windows XP platform.