Europa Barbarorum is a total conversion modification. The modification affects all areas of RTW; all vanilla units have been removed, all new models and textures, a new economic system, new traits system, new scripts, and in general new gameplay. No area of RTW is left untouched.
Roma Surrectum 2 is a full conversion mod to Rome Total war 1.5 and the predecessor to the original Roma Surrectum mod featuring unique Roman legions, new factions, units and a stunning high detailed map. Roma Surrectum 2 is developed for Rome Total war, but it will also run on both of its expansions, Barbarian invasion and Alexander.
<path-to-game>\Rome Total War Gold\data\fmv
You have installed Rome Total War on a 64-bit system, but there is a bug in the installer which installs the game files in the wrong location by default. The incorrect default location is C:\Program Files; the correct location to install these files is C:\Program Files (x86). To fix this uninstall Rome Total War and all its expansions and patches, then freshly install the game again, making sure to installer selects "C:\Program Files (x86)" to install the game to. Warning: uninstalling the game and its expansions and patches will delete any saved games, the save game data folders should be copied to another destination and replaced after the fresh install.
C:\Program Files (x86)
A fix is to copy the steam.dll file from the main Steam folder into the Rome installation folder. This is a fix that most likely will fix your problem.
This issue is common with the Steam version of the game, with the error window appearing when attempting to launch either Rome: Total War or the expansion Barbarian Invasion.
...\Program Files (x86)\Steam\
A less problematic fix that works for some people is disabling the steam community for this game.
If neither of these methods work or if you are getting a "Steam failed to start" message, exit Steam then right-click the Steam shortcut and choose Run as administrator.