Move the ROM image to a location where the path is very short (such as right after C:). If the editor won’t run, please do the following. A level editor for Rockman 2 and Mega Man 2.
This option is also accessible in the Mega Man X Collection for PlayStation 2 and GameCube: after selecting X2 on the game select menu, hold the jump button (on SNES, B is by default the jump button) on the second controller. It doesn't change anything gameplay-wise, since it was a developer's tool. To access this test, hold B on Controller 2, then power the system on.