Semi-transparent background form with opaque icons

Hi All.

If you look at the MacOS X dock, the buttons (fully opaque) are sitting
on a semi-transparent background. How do you achieve this affect in
WinForms?

I have a form and set its opacity to 50%, but then when I place buttons
on it (that contain images), they too also appear at 50% opacity.

How can I have opaque buttons on a semi-transparent form?

The information contained in this e-mail message is PRIVATE. It may contain confidential information and may be legally privileged. It is intended for the exclusive use of the addressee(s). If you are not the intended recipient, you are hereby notified that any dissemination, distribution or reproduction of this communication is strictly prohibited. If the intended recipient(s) cannot be reached or if a transmission problem has occurred, please notify the sender immediately by return e-mail and destroy all copies of this message. 
Thank you.