This might help :
MacBook Tray Tools - Drivers for keyboard backlight and sensors of your MacBook / Pro.
Quote:
What is it?
If you happened to be a happy MacBook
/ MacBook Pro owner running Windows
with Bootcamp, you surely felt annoyed
of current lack of driver support for
some neat features offered by this
beautiful piece of hardware. For
example the keyboard backlight and
automatic brightness adjustment based
on environment light is completely
lacking any drivers. How long would it
take for Apple to release the complete
set of drivers and how well the Apple
hardware will be supported under
Windows compared to Mac OS X, nobody
can say for sure. The recent release
of Bootcamp did not include this
support.
I put together a small tray resident
application which lets you activate
and control the keyboard light, it
also accesses the light sensors to
resemble the automatic light
adjustment to the environment light as
you know it fromMac OS X.