I will describe a few simple steps to perform a hard reset on the Lenovo A660:
1) Turn off the device if it is turned on.
2) Press the volume down button and the power button at the same time, wait for the recovery menu to appear (Recovery mode).
3) In the recovery menu, press the volume button up/down to highlight the item “Wipe data/factory reset” and select it by pressing the power button, in the next submenu, select “Yes” by the same method.
4) Upon completion of the cleaning, the recovery menu will be displayed again, in which we select the “reboot system now” item, after which the device will reboot.
Done.