I haven't used their downloader. I've always downloaded the files manually and then run the Setup to install the game. Then when running the game for the first time, I have to enter the code for it to activate.
I found some instructions for using the downloader ***here***
, which seem to be what you're doing.
It's possible that your computer may be blocking the game from installing through the downloader. If you can locate where the downloader put the game's installation files, try running the game's installer manually. I'm sorry I don't know where the downloader puts the game's installation files in Windows 7.
If you want to try downloading and installing manually, there are instructions ***here***
(hope the link works).