Okay, I tested the majority of it yesterday and everything seemed to work excellently.
Do note, however, that this is the file for the US version of the game. I'll try and put together a second download for the UK w/ bonus scenario version soon.
You can download the modified .exe file
hereInstructions for downloading from RapidShare
~ Click the above link
~ Scroll down to the bottom of the page and push the button that says "Free"
~ In the middle of the page you should see a counter... wait for it to hit 0, then pick a mirror (doesn't matter, but pick the one with the lowest number for faster speed)
~ Enter the 3 digit letter code into the box and hit the Download button
Once you've downloaded the file...
~ Extract the modified .exe file to the folder
C:\Program Files\Empire Interactive\GhostMaster\GhostData~ Double-Click the modified .exe file (its named All-Ghosts Mod.exe) to start the game
~ Once you've got the game running, start a New Game. You cannot use a previous save because of the way the information storage is handled.
~ Gameplay will be completely normal, except that when you go to replay levels you'll be able to use any ghost that you've already obtained
Note: Make sure you start the game with the modified .exe file each time, at least until you have all of the ghosts. Once you get all ghosts and beat the game, you can use the regular .exe file if you so choose, but its easier to go ahead and start it with the modified file as long as you want all the ghosts.