Eventually I managed to "disable" a few lines of code in the compiled exe.
I used Reflector with Reflexil plugin installed. Reflexil allowed me to edit an MSIL instruction, and then save the result back to an exe file. So, it involved learning a few MSIL instructions, especially the "no operation" command (making a line of code do nothing). To see the list of instructions and a tutorial, see here and here.
Hope it helps someone else.