Hard Reset HTC One SV

First method:

1. Turn off device by holding Power button.
2. Press and hold Volume Down + Power button until you see three Android images. 
3. Now select option "FACTORY RESET" to browse use Volume buttons, and to choose optionPower button. 
4. Phone will reboot.

Second method:

1. Go to Menu -> Settings -> Backup & reset.
2. Find Reset phone and select it.
3. If u want delete all data (all the media) select Erase all data.
4. Push OK button.

WARNING !
Hard Reset will erase all of your data
All described operations you are doing at your own risk.