You can use FCEUX's debugger, that's one possibility. No .nes file I've ever heard of is "locked up." Any emulator that has a debugging feature makes it pretty easy to see the code in a game. To actually read and understand it takes a lot of work if there is no source code available. For my homebrew titles, I always have the source code available and can tell emulators to actually insert my labels/comments amongst the 6502 instructions and data for easy debugging. But for any old .nes file, be prepared for an adventure.
Edited: 02/12/2013
at 08:16 PM
by GradualGames
