HexCheats:

 Edit the file aitd3.exe with a hex editor and search for the hex
 combination 26 29 07 E9 3F 02 C4 1E and change these offsets
 to 90 90 90 E9 3F 02 C4 1E. You are now 'undead'.

DebugCheat:

 Play the game as usual and create a save game in slot 1, quit to DOS
 and type the following at the DOS prompt:

 DEBUG
 NSAVE0.ITD
 L
 EAE64 00 40                  For maximum health
 EB0CE 00 40                  For the 38 Special
 EB0C6 00 40                  For the Winchester
 EB1C0 00 40                  For the Gatling Gun
 EB16A 00 40                  For the Shot Gun
 EAE7A 00 40                  Health after returning from the dead
 EB1EA 00 40                  For the Colt
 W
 Q