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Clearly there is a large base of general knowledge that I don't have.  Please indulge me.  I have a Garmin foretrex 401.  I've loaded an application called Garmin Basecamp onto my laptop.  I'd like to be able to open maps into the application and mess with them:  view details, plot stuff using the app, do markups and labeling, print edited maps, etc.  From this website I've downloaded a folder called ortopo11.  The folder has a number of  .img  files, named with 8-digit numbers.  The default type of the file icon invited me to "burn an image" to a dvd - tried but was told the file type was invalid.

I guess I'm presuming that what I downloaded is somehow accessible to Basecamp.  I don't know how to view the content of a .img file nor how to open this mysterious content in the Basecamp application.

What gross ignorance have I revealed?   Can you help me?