I have an android smartphone that streams audio via Bluetooth.
I want to play that audio via a PC running Windows Vista. What software would you recommend to install on the PC side?
Try BlueSoleil, it should support it if you enable the Headset AG service.
It would help to know some details about your smartphone and your PC.
In theory, you don't need any software on the PC. You just need to enable Audio Gateway or something similar on the phone. Then on the PC it will become available in Control Panel / Sound, so you could use it in your player if it's sophisticated enough.
However, between theory and practice there is a big difference ...