HTC One M8 for Windows - Manual (Page 173)

Unpairing
If you no longer want to use a connected accessory with your phone, you
can unpair and remove it from your phone.
Make sure to disconnect the accessory before unpairing.
1. Swipe down from the top edge of the screen with one finger.
2. Tap All settings > Bluetooth.
3. Press and hold the name of the accessory, and then tap delete.
Connectivity 173