Man, I really need to only help people when I'm at home where my games are. ^_^;; I'm so sorry, forgive me!
OK, the ALSignup was part of the download package, you should have gotten the ISO, and a folder called "alsignup_100723b crack".
That folder contains the "alsignup_100723b.exe" file, and two other important files named ".data" and ".text".
Those files need to be moved into the same folder as the Omerta game, then follow the rest of the post above to finish installing.
Try doing a search on your computer for the file "alsignup", and if it doesn't pop up you may need to download it. I don't know if someone has just that set of files posted, as most places seem to have the ISO + Crack combo pack.