i have the MS bluetooth dongle which i got with their optical desktop set...
but i presume it comes with just the mouse.... although i am not sure how
much it costs or if it can be bought individually
You may be able to get Bluetooth working by manually selecting a driver for
a similar sounding device. For example, if you've got a Broadcom device
(many Acer laptops), you can manually select the appropriate Broadcom
Blutonium device in Device Manager.
That's how I got my Bluetooth working.
-- this post brought to you via a BT keyboard via the Broadcom bluetooth
module that was enabled this way