Had the same problem when I installed W7 in my mac mini. It was a pretty simple fix. Worked like a charm. Hope it resolves your issue(s).
Follow these tips while you are in Windows 7 :
1) Switch off the device you want to pair
2) Select "add a device" in the Bluetooth menu
3) Switch on the device (after few second it should get detected by Windows)
4) Now, right click on the device and select properties. You should now get a window with the different services.
5) select the HID drivers for keyboard and mice and click OK (this is the important part)
6a) In windows 7 it should setup mouse and keyboard without any additional input
I found that tip posted by S_ Eye at
http://discussions.apple.com/thread....art=0&tstart=0
Good Luck.