If you want to pair Bluetooth headset with or any other Bluetooth accessory like Speakers, car kits here is the guide to Pair Bluetooth device with Windows Phone 7 mobile.
Pair Bluetooth Headset with Windows Phone 7 Mobile
Tap “Arrow” on Start screen or Slide to left on Window Phone 7 mobile.
Tap “Settings” then “Bluetooth” menu.
Turn the Bluetooth status On by tapping on On/Off Button.
This will start searching for Bluetooth devices (Make sure your Bluetooth headset is Turned On and discoverable).
Tap the Bluetooth device that you want to pair with Windows Phone (If you need to enter a PIN to pair, use the same PIN on both devices your Phone and Bluetooth headset).
Unpair Bluetooth headset Windows Phone 7 Mobile
Tap and hold the name of Bluetooth headset in Bluetooth settings and then tap “Delete”