Background Vista Sidebar

Does anyone know whether it's possible to change the background color or
transparency of the Vista sidebar?

After first installing Vista, it was entirely transparent, but then became
(and still is) a gradient, going from transparent on the left to almost
entirely black on the right. Quite frankly, this looks horrible and makes you
think there's something wrong with the screen. Anything but a gradient (i.e.,
image, colored background, or fully transparent), would be a 1000 times
better.

Detaching gadgets to put them elsewhere on the desktop isn't an option, as
they become bigger, which is not what I want.
--
Luc

I don't see a way to change this on its own, but if you feel strongly,
you could change to the "Windows classic" theme. It looks a bit retro
at first, but it has exactly the same functionality as Aero, without
the unnecessary prettification. It runs faster as well.

By design the sidebar is transparent, meaning it will take on the
colors/design of your chosen background underneath. You can override
this by using the sidebar options electing to have the sidebar always
on top. If set this way then the sidebar area takes on a different hue
and will be more opaque.