Sizeing windows in Win 7

Hello,
I am using a program which is a compilation of some e-books. The books can be accessed only after installing the program. When I used this program in Win XP, the program window could be maximized to full screen size. But in Win7, it shows a small window which cannot be resized. I am using a wide screen Inspiron Dell laptop. Is this Win7 issue or laptop screen resolution problem? I also tried to change screen settings. Resolution is set to highest (1366x768).Can anybody help me with this problem? It is very irritating to read books in a small window. Thank you. :)