This is my fix to get my Motorola PC850 Bluetooth dongle to work with Vista.
This was done and tested on Vista Ultimate 64-bit edition.
Once you insert your PC850 windows will be unable to find a driver for it.

When it prompts you for a driver choose:
"Browse my computer for driver software"

Choose "Let me pick from a list of device drivers on my computer"

- Here choose GenericAdapter under manufacturer list
- Now choose Generic Bluetooth Adapter
- Click Next

Windows will give you a warning that this driver is not recommended for ....
blah blah blah...
Just click "Yes" to continue using the driver.
You should now have a bluetooth tray icon.

Now you can add bluetooth devices and they will work!

This is what your adapters properties should look like.