Prueba esto -
http://www.mediafire.com/?tt7jc85lgy5rm4k - a ver si te funciona, yo no lo puedo probar ya que tengo el teclado con cable de mac ...
EDITO: También he encontrado esto a ver si te vale, sin tener que instalar nada ...
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)
6) In windows 7 it should setup mouse and keyboard witho
Si quieres te lo traduzco.