I have a Motorola HS820 and a DLink DBT-120 using Widcom drivers. That works for Skype and Ciscophone, as well as Windows audio.
Turn your cellphone off, or disable the Bluetooth. Turn the HS850 off, then hold the button until it blinks, and then turns steady. At that point, you should "view devices in range" in My Bluetooth Places.
The Motorola Headset should appear. A double-click should prompt you for the PIN code, which is 0000. Once you pair, you don't need to repeat that step. Power on the HS850, but don't force it into pairing mode.
The HS820 should emit a double-beep every couple of seconds, indicating an incoming connection. Press the button like answering a call, and you should now be an audio device to Windows.
control-panel-sounds would let you select the Bluetooth Audio as the default, which might already have happened. Some other sound program, like Skype, lets you select which audio device you want to use.
start-programs-accessories-entertainment-sound recorder should let you do some testing.
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