Problem transfering to Nook Color

I've been pulling my hair out over this for 2 days now.  I used Overdrive to download an ebook to my PC.  I then realized that the file was not readable by my device.  Then I downloaded Adobe Digital Editions to my PC, authorized both the computer and the Nook, and have been unable to move the ebook from ADE to the device.  The "copy to device" feature shows the Nook as greyed out.  I'm stumped after searching Overdrive and Adobe, as well as the Web generally.  Has anyone got a clue how I can get this to work?