Factory Reset (Hard Reset) HTC Butterfly

Software reset will return your device to its default settings. Like a brand new phone, no information or data saved on your device. This procedure will erase all your data save on your phone.
If your phone is frozen, it is recommended to perform the Hard Reset. You can soft reset your phone in two ways. By accessing it through settings or doing the hard key combination.

Resetting HTC Butterfly on Settings :

Slide the Notifications panel open, and then tap the Gear Icon or Settings.

Select Backup & reset.

Tap Reset phone. 

Then tap Reset phone, on the Reset phone screen.

If you want to delete the files on your HTC Butterfly, tap OK.

Resetting HTC Butterfly by Hardware Buttons:

These steps is also helpful when your HTC Butterfly is unresponsive or frozen and there's no way to access the settings.

First, press and hold the Volume Down button, and then do the same way on the Power button.

Hold the two buttons until the three Android images appear on the screen. 

Release the button when the three Android images appear and press Volume Down.

Tap on Factory Reset, and then press the Power Button to confirm.