Ever since the release of windows 95 it has been possible to minimize the volume control:
In Vista, the minimize button was removed for no reason. Why Larry, why???
Adding the window style back with a tool like WinSpy++ clearly shows that there is no technical reason for the removal.
Even adding the maximize button works. (I have a little program that runs in the background and fixes little annoyances like this, when I get around to talking about the stupid vista explorer tree view, I might talk more about this tool and what it does)