Always make a backup copy before making any changes. Rightclick on the file 'OPTIONSGENGAME.IDS' which will be located in ..datainterfaces. Click on Properties and remove the readonly attribute. Now open the file with any text editor and add the following lines to the bottom:
BUTTON CHEATBUTTON 155562255582
TEXT BFONT 0 255255255255 "CHEAT MODE"
ONBUTTONUP SWAP OPTIONSMISC.IDS
This will enable the cheat mode button on the general options.