Re: Problems downloading on Steam
Are you using Windows 7 or Vista? If so, first disable UAC. (see here) Then do it like this:
Completely uninstall and remove any TATW related files.
Install all parts of TATW (3.0 Part 1, 3.0 Part 2, 3.1, and 3.2) to the desktop.
Then move the Third Age folder to the Steam/Steamapps/Common/Medieval II Total War/mods folder.
Then rename one of the Kingdoms campaigns to something else, like change americas to americas2.
Then rename the Third Age folder to americas. Finally, select the americas campaign from the Steam menu and the mod should launch.