How to get HP 2009m monitor to work with macbook?

So, I bought this HP 2009m external monitor to use as a secondary display for my macbook, running Mac OS X 10.5.8, Leopard. In the reviews of the product, several people had said that the monitor works fine with their own macbooks. However, when I connect the monitor to my macbook via an Apple VGA-to-MiniDisplay Port adapter, the monitor goes directly to sleep, and the monitor says its receiving no VGA signal. I connected it to my PC laptop and the monitor works fine. Is there anything I'm doing wrong or something else I can try? Any help or advice would be appreciated. Thanks.