you've got the bluetooth profiles wrong.
headset and handsfree are low-quality mono audio profiles, used for making calls and connecting with your average cell phone BT earset.
A2DP is the Advanced Audio Distribution Profile, and only compatible with later BT stacks. Your computer might not even support it.
If it does, it will be called something like Wireless Music, or A2DP/AVRCP, etc.
If you want to use the sub-par headset or handsfree modes, the PPC is smart enough to assume that you don't want your music to sound like its coming out of a tin can (the quality is good enough for a cellular phone call, but not for music), so it only routes phone calls to the headset.
There are a few ways to force all audio coming from the ppc to the bt headset, such as using the app BTAudio to toggle it. In order for this to work, you still need to set your PC to be an AudioGateway, which is different from headset/handsree (more specifically, headset is to output mono bt sound to an external speaker, and handsfree is the same thing plus support for handsfree controls such as redial, voice dialing, etc. If you want your PC to be the one RECEIVING audio instead of sending it to a headset, you need the Audio Gateway profile).
If your pc supports A2DP input, then you're golden. Many PC BT stacks pre-date A2DP, and the ones that support it usually only support output. But you can check.
In the end, you could always get yourself an A2DP BT Audio receiver like the i.tech R35, and plug them into your speakers. That's what I did to play music over my home stereo.
