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 e:\raider.exe cheater.cht
 debug e:\cheater.cht
 e 1460 f8 c3
 e 920 90 90 90
 e 901 90 90 90
 w
 q

 Then rename CHEATER.CHT back to its previous name.