@mouettefluo I'm not surprised that mounting the ISO wouldn't work. Does it make a difference if you use one of the executables within Program Files to start the game? If your install isn't controlled by Origin (as in, you don't need to have Origin open to play), you'll want TS3w.exe, or maybe something like TS3EP03.exe for Late Night (it's newer than High-End Loft Stuff, so it runs the game in some ways.) The .exes will be in the Bin folder for the base game or for Late Night.
If this doesn't help, you could always install the game through Origin, if you haven't already. If you have, just uninstall Late Night and reinstall it through your Origin library, no need for a disc. You'll need to launch the game through Origin, or through TS3.exe (or a shortcut, and no W in the name this time), which would bring up Origin and then the launcher once you sign in.
If you're not using Origin and would rather skip it, and launching through the .exe doesn't help, let me know.
