What Is a Bluetooth Stack?
A Bluetooth stack is an application installed on your computer that interacts with your Bluetooth devices. Two Bluetooth stacks are widely in use today:
The Microsoft Bluetooth stack, which comes with Windows XP Service Pack 2
The Widcomm Bluetooth stack
Most Bluetooth adapters use the Widcomm Bluetooth stack driver. Widcomm (acquired by Broadcom, http://www.broadcom.com)
licenses its software to most Bluetooth manufacturers. Consequently, the installation, configuration, and use of different Bluetooth devices on Windows have a nearly identical look and feel.
The problem with the Bluetooth stack built into Windows XP SP 2 is that it has limited support for profiles. In particular, it does not support the Headset profile required to connect with Bluetooth headsets, and hence your Bluetooth headsets will not be able to work with your Windows XP PC.
To overcome the limitations in the Windows Bluetooth stack, you can install the Widcomm Bluetooth stack drivers from the manufacturer of your Bluetooth device. You can download the latest drivers and support software from the adapter vendor's web site. Because each vendor customizes the Widcomm software slightly, you should not use drivers from a vendor other than the one that manufactured your Bluetooth adapters.