I tried using ROFL Copters guide but its outdated since steam was changed. I did though use something from ROFL's guide so i wont be taking all the credit
Hope that this will get stickied to help in the future.
Guide:
1. open steam.
2. right click on Rome: total war - Alexander.
3. click properties.
4. Under General tap there should be something called "set launch options..."
5. write this "-applaunch 4770 -nm -show_err -mod:aristeia" without the quote marks. then OK.
6. Go to the Updates Tab next to General. Open the slide down and click on "Do not automatically update this game" and then close in right corner.
7. run the game via Rome: total war - Alexander in steam.
(8, not a must). IF you want to play Rome total war - Alexander, just delete "-applaunch 4770 -nm -show_err -mod:aristeia" and copy it to a notebook on desktop or something, so if you want to play it you can just follow this guide again.
Have fun playing!
Note: I used "-applaunch 4770 -nm -show_err -mod:aristeia" from ROFL Copters guide.
Kind regards, moizzz