@Tuono, that .IMG file is not to burn on CD.
It's a map file with .IMG extension, for Garmin GPS software. I think you already know that.
You put that file in your GPS, in Garmin folder, and you can navigate in Bulgaria.
Maybe already you have in your GPS, a file named gmapsupp.img. It's another country or more.
Rename your existing gmapsupp file, and put the new gmapsupp.img file in Garmin folder.