To me it seems that your MTW 1.1 files have not been replaced with the mod files if you just get MTW 1.1.

Unzip the mod files somewhere else.
Then change the name to "medieval - Total War", if it is named "Redux - Total War", otherwise leave it the same.
Then drop it (or copy it) in the "Total War" file in "Program Files" (if you have installed MTW 1.1 in the automatic way).

This "should" do the job.
Are you shure you upgraded to 1.1 (check in the options menu after opening the game what version it tells you it is).

Hope this will help. Otherwise Ax will have to do the work.