When you connect a Bluetooth audio device to a Windows Vista-based computer, the audio output is not automatically routed to the Bluetooth audio device.
This behavior occurs because audio devices in Windows Vista do not dynamically switch when you add a new device, such as a Bluetooth audio device. This is by design.
To work around this behavior, set the Bluetooth audio device as the default audio device in Windows Vista. To do this, follow these steps:
- Click Start and then click Control Panel.
- In Control Panel, click Hardware and Sound.
- Under Sound, click Manage audio devices.
- In the Sound box, click the Playback tab, select the Bluetooth device, click Set Default, and then click OK.
- Restart all the multimedia programs that are currently running.
Microsoft has more details here: