|An .exe file contains the object (runable) program.|
This may have started life by being written in a programming language. The file containing this is called the source.
The source is compiled into the object.
Trying to reverse engineer, can be likened to being as difficult as squirting milk back into a cow's udder, then converting it to grass coming out of its mouth.
Do you have access to the source program?
Do you know in what language or application the object program was created in?
There is an article on watcom on wikipedia and also there may be a useful contact here:-
Please advise back on progress.
Good Luck - Keep us posted.