This is fairly straightforward. Go to the game's Steam directory, find the file "nukem.bat" and change the name to "nukem.bat.txt"..or simply opne it with a text editor...and where it says "dn1.exe", "dn2.exe", and "dn3.exe" add a single space and without quotes add "asp" at the end of those lines. Then save and rename the file back to "nukem.bat"...and yes click on "Yes" when warned about the dangers of file type change...

Example code (WITHOUT QUOTES):

"dn1.exe asp"


You are now ready to cheat....

fold down G+O+W to skip to the next level...

Hold Down G+O+D for full powered nuke gun, all items, health and keys.