Let's focus on one problem at a time.

Do not try to open the .bin files - they're archives. You need to launch the .exe file.

Make sure that you've got a lot of free space on your drives when you finish downloading - the Downloader will need it in order to merge the files.

After the Downloader merges the files, it checks the merged .bin and .exe files' integrity. This means it's impossible for corruption to happen on the Downloader's end. In such cases I suggest checking your hard drive for errors (Scandisk, thorough scan) and your RAM as well (memtest86, bootable CD).

When launching the installer, make sure that your user account has Administrator privileges and that User Account Control is disabled in your operating system. To do this, go to Start -> Control Panel -> User Accounts and Family Safety -> User Accounts -> Change User Account Control settings. Move the slider to the lowest position ("Never notify") and click OK.
Afterwards, launch the installer by right-clicking its shortcut and selecting "Run as Administrator" and let me know if that helped.

This shouldn't be possible if you used the Downloader... Don't hate me for this, but can you try redownloading the game from scratch?