Adobe Digital Editions 4.0 does not recognize my Toshiba Thrive tablet so I cannot transfer an ebook to it.

I have tried everything I know and guessed at in an effort to get a book from my PC to my Toshiba Thrive tablet.  The Toshiba Thrive is, of course, not listed among the transferable devices that are given in the directions.  So, where do I go from here?  I do have it on my PC but would prefer reading it on my Thrive.