Mike,
If you are talking about the actual window being missing then all you need to do it go to the Window Menu and under Window Settings click Reset Default Layout. This will return Maximizer to its factory default windows layout and should display the Company & Contacts windows.
If you mean that there is no data in the address book window, this is because Maximizer is a database driven application and it doesn't automatically retrieve records on startup unless specifically told to. In this case you should go to the Search menu and click on Company. Then leave the criteria field blank and make sure the Maximum Number of Entries is set to All. Then click ok, this will return all the Company records in the address book.