I think you should try the driver coming with boot camp 2.2 update package. I also have a 2-batteries keyboard, and turns out it works with this new driver.
driver is attached
Here is what I can tell about a Samsung Q35 Notebook with Win7
I have 2 apple alu wireless keyboards.
(They look the same !! But only from the outside !!!)
One uses 2 batteries
One uses 3 batteries
The one with 3 batteries is recognized in Win 7 (everything, fn-delete for del, volume up/down, eject) with all the nice images that pop up, when you push a special button. In the drivers settings I can see that Win7 chooses the Apple Bootcamp driver.
The one with 2 batteries on the other hand, well, it doesn't like me. I have tried so many things. It only works with the Windows drivers (so no special keys and no keypush-popups) and no matter what I tried, I couldn't make Windows use the Apple Bootcamp driver it uses for the other (so identical looking) keyboard.
Also found an Apple Support entry, that might be related
If some still finds a way to get the 2 battery mac wireless keyboard working on win 7 on a pc (not mac).... Please tell me how.