The Mega Man 4: Free of Charge download comes as an IPS patch file. There are free utilities out there like Floating IPS that can apply the patch file to a clean dump of a NES cartridge.

Wily's Fortress: Part 4 Stage Map by KeyBlade999 67K Maps and Charts Elec Man Stage Map by KeyBlade999 ... Map by KeyBlade999 118K Maps and Charts Mega Man Series Boss Chart by MetroidMoo 57K ...

Capcom released the Mega Man series in 1987 with the NES game Mega Man. The hero, a humanoid robot, was created by Dr. Light to save the world from Dr. Wily and his rebellious robots. The player ...