I recommend following:
- download CNNA_13.20_MS from post #1 - these are fast zippyshare links
- extract downloaded archive with WinRAR or 7zip
- the map has to be unlocked with UnLock MapSource Directory - copy it inside the subfolder \IMG\City Navigator North America NT 2013.20.gmap and start it with admin rights
- install the package with CNNANT2013_20Update.msi in subfolder \IMG\
You will get the programs BaseCamp, MapInstall, WebUpdater and the North America map installed on your PC - then you can create your own map image with MapInstall and send it to your connected device or SD card