Start on Various Levels:
Use these command line switches to start on a certain level. You will have to make a shortcut and edit the properties to something like pop3d.exe -l "geometry\rooms\prisonfix"

You will only be able to go to 1 level at a time with this cheat.

Other Levels:
-l "geometry\rooms\prisonfix"
-l "geometry\rooms\ivorytwr"
-l "geometry\rooms\cistern"
-l "geometry\rooms\palace2"
-l "geometry\rooms\palace3"
-l "geometry\rooms\palace4"
-l "geometry\rooms\roof1"
-l "geometry\rooms\cityanddocks"
-l "geometry\rooms\dirig1a"
-l "geometry\rooms\dirig1b"
-l "geometry\rooms\dirig2"
-l "geometry\rooms\dirigfinale"
-l "geometry\rooms\ruins"
-l "geometry\rooms\cliffs"
-l "geometry\rooms\solar1"
-l "geometry\rooms\moontemple"
-l "geometry\rooms\finale"