Uninstall RTW and delete the RTW folder out of the activision folder, then restart and install RTW again... Then once it's installed add the 1.2 patch.

Mod downloads sometimes get corrupted if you do other things whilst downloading it... Like if you download other things at the same time or keep changing websites... Whenever i download anything like that i just leave the computer and sign out of all messengers and stuff... But you'll just have to delete the corrupt one you downloaded.

Good luck!