Error editing PBMs

When I open Title.pbm in Photoshop I get the error 'Could not complete your request because the file-format module cannot parse the file.'. When I make a new image and overwrite that pbm, the game doesn't start.

Does anyone know how to fix this? ^^;

 

PBM files must be renamed to BMP before you attempt to edit them.

After you save the edited version, you must open the file in a hex editor, add (C)Pixel to the end of the file, and then rename it to .PBM

Then it should work.