My Dear Wordwind:

Go to http://www.atomica.com/

Click on download; it's free. Then, all you will have to do is to put your cursor* over a word that you want to look up, and press Alt--a little dictionary window will pop up, with your word. And it does more than a dictionary, too.

*Let me clarify--you must have the word on your screen, which sometimes will necessitate typing it, or as close as you can get to it.