Not sure how aware you will be of this, but editting .exe files could easily be quite prone to breaking them - they are the machine code level and unless you are fluent at that level you should think twice about editting them. Of course there may be parts that are responsive to editting - like changing icons or filenames, where the .exe file is referencing a constant within the code. Even then there could be unforseen consequences, depending upon how the code has been written.
The best option is, prehaps, to start with source code. If the .exe you require is not open source then tis could mean writing your own program to do the same as the .exe does though.