"Microsoft has created an update for system and device manufacturers that adds native support in Windows XP for Bluetooth wireless technology. This update permits Windows to work with several types of devices that implement Bluetooth wireless technology, such as personal computer peripherals and personal computer companions. This update can be distributed to customers under license agreement with Microsoft... If you are not a system or device manufacturer, contact the manufacturer of your Bluetooth wireless technology device to obtain this update."
You have to contact the manufacturer to get this file.