If you are still using Windows XP and refused to upgrade to Vista (and probably waiting for Windows 7 to release later this year), you would realize that Win XP does not allow you to use headset profile (mono or stereo). It is because Microsoft did not include those profile stacks in Win XP and never bothered to include them in the subsequent Service Packs!
As a result of that, you cannot enjoy neither mono nor stereo sound on your computer even though your laptop/pc comes with built-in bluetooth (especially true for Macbook/Macbook Pro/Macbook Air).
The solution is first proposed by U.C. and further explained by reesd at InsanelyMac forum. I decided to combine their solutions to make an easy-to-understand step-by-step guide.
Also, this guide deals primarily with getting those profile stacks installed on Mac computer running boot camp in Windows XP. However, it also works with any laptop that has built-in bluetooth.
1) Download the Toshiba bluetooth stack profile and driver from http://aps2.toshiba-tro.de/bluetooth/?page=download
*Please know that the Toshiba Bluetooth Stack only valid for 30 days. After that, you would probably have to purchase the software in order to continue to use it. HOWEVER, if you are savvy enough, you can search and download it from torrent site.
2) Install the Toshiba Bluetooth Stack. It will reach a point where it tries to find for a compatible hardware, but cannot find it. Click "cancel".
3) Go to Device Manager and look up your built-in bluetooth device info under Bluetooth (the device is probably called Apple Bluetooth). Look for DeviceID and copy the info down.
For example, my DeviceID is USB\VID_05AC&PID_8205
4) Browse to the folder "Program Files\Toshiba\Bluetooth Toshiba Stack\Drivers\tosrfusb"
5) Open tosrfusb.inf file using notepad or any text editor.
6) Scroll down the file to the middle until you reach [Standard] section. You will need to assign a new number that has not been taken by other items in the [Standard] section.
For example if the list has up to 140 items, I will type in the following line after the line %TosrfUsb.DevicDesc140%=TosrfUsb_Device, .....
7) Scroll down the file until you reach [Strings] section.
Type in the following line after line
TosrfUsb.DeviceDesc140 = "xxxxxx"
TosrfUsb.DeviceDesc144 = "Apple Built-In Bluetooth Toshiba"
8) Save the tosrfusb.inf file and reboot your computer.
9) Return to Device Manager. Select the first Bluetooth device and choose to Update Driver. Don't let Windows search for the driver, but choose the option that you want to search for the driver on your own.
You will reach a point where there is an option "Have Disk". Click it and select Program Files\Toshiba\Bluetooth Toshiba Stack\Drivers\tosrfusb as the directory.
It will prompt you about unsigned driver. This is because you have edited the .inf file. Proceed with the driver update.
10) With the update, you can click on the toshiba bluetooth icon on your taskbar. Enable the bluetooth and choose new connection to search for your bluetooth device.
**The usual default passkey for pairing bluetooth devices is 0000 (as in four zeroes)
***I assume you know how to set your bluetooth device to pairing mode. If not, read your user manual. It is usually by holding the power button on your device for a certain amount of time (a couple of seconds) until both LEDs blink continuosly (usually red and blue)
****Handsfree (hf) is a newer mono bluetooth profile than Headset profile. Both are mono audio, but handsfree seems to support more options.
11) After you have paired the device to your built-in bluetooth, you can go to Bluetooth Settings (or double click on the icon on taskbar), double click on the selected bluetooth stereo device.
*****If you are using A2DP and the audio skips, go to Bluetooth Settings->Right click on your paired device name->choose a lower Quality setting such as Standard to see if there is any improvement.
12) Enjoy your full headset/A2DP/AVCRP support on Windows XP! (for up to 30 days or unlimited if you decided to torrent)
13) To disconnect, go back to Bluetooth Settings and right click on the bluetooth stereo device, choose Disconnect.
Note: Another software that enables A2DP on Windows XP and Vista (non-mac) is covered here.