To enter the codes you have to get a fax first. Press the green ? button that shows up from time to time at the bottom of the
screen to get to it. Then just use the mouse to press the numbers on the fax machine and press the send button.

     7827 - After you win the level go to a rat shoot level 
     24328 - Enable the following codes during gameplay 
     SHIFT-C - Get $2000 
     CTRL-C - All research completed 
     CTRL-M - Skip to the end of the month 
     CTRL-Y - Skip to the end of the year 
     CTRL+S - Doctor with special stills 
     CTRL+E - Makes one emergency 
     SHIFT+1 - Extra patient 
     SHIFT+I - Change patients illness 
     F11 - Level lose 
     F12 - Level won 

To start on a specific level use this command line switch: -Lx Where x is the number of the level you want to start on 
After typing 24328 at the fax, when playing normally press Ctrl + Shift + C. This will give you all items. We have tested it + it
works.