For invulnerability in this game, use the DOS utility DEBUG. First
 backup your game to be edited, then type the following from the DOS
 prompt: 
 
 ren mach3.ov2 cheater.cht
 debug cheater.cht
 e 261f 90
 Then type: w
 q
 
 Then rename CHEATER.CHT back to its previous name.