question about mini dvi to dvi

I recently bought one of thse mini dvi to dvi for my macbook from ebay. I'm not sure if theres a setting I have to enable to click for it to view. But basicly i plugged it into my macbook and the other end i had my monitor's dvi plug in. Nothing is showing up on my monitor, but i can still see from my macbook.

Did i miss a setting somewhere or is this just a doa?

Did you check in the display settings. I'm sure you must have. Though, the macbook mirrors its display so there should not be any setting to enable the second display as such...