Steam downloading help

[chris150150]

I am trying to download this game since it looks amazing, but when I install it to

C:\Program Files (x86)\Steam\steamapps\common\rome total war gold

and click the launcher option a message comes up saying "C:\Program Files (x86)\Steam\steamapps\common\rome total war gold\RomeTW-AKZ.exe is not a valid win32 application." (Without quotes) I googled how to install steam mods and read a topic on the forum here, but it doesn't help. Anyone know a solution.

Thanks,
Chris

***Edit***
My computer is a 64 bit, so I don't know why it says it isn't a valid win32 app. I also googled why the message would come up but they all seem not to be happening.