One thing I did: I disassembled an executable (Battle Chess), figured out data (text) mistaken as source. Once all those fake sources were converted into data, I could reassemble/add/remove stuff.
This is the easiest (sometimes there are even symbols left in the executable
). If you need to hack NDOS games, the best is to improve existing whdload installs, as whdload slaves are designed to patch games easily.
There are a lot of slaves with enhancement requests, check whdload mantis for this.