ASSUMING THAT WHATEVER YOU'RE DOING IS LEGAL (and that you REALLY don't know what a crack is, though that made me lol a bit), Go to Program Files. Find a folder that's named after tha game, or after the creators of the game (i.e. Final Fantasy VII would install to "Program Files\Eidos Interactive\Final Fantasy VII" by default).
If this doesn't work for you, here's an easier way of doing it: just right-click the shortcut to the game/program in the start menu, hit "Properties", and then click the "Find Target" button, and the folder with the actual executable will come up. Now you can freely paste your updated executable.