Which file did you download and where did you download it from?

(Generally) "The "download managers" are small (typically approx. 4MB). When run, they will fetch a much larger (e.g. 400-450MB), main installer for the current release, along with other bundled plugins and apps."(Or) "You can install any release directly from the "larger" (~400MB+) direct installer if you have it, and links to those are sometimes included in the new update posts in the NEWS forum." (From the FAQ)