(Warning! When you do a full reset, your LG Smartphone returns to its default settings and looses all data that is stored in your phone. Do not forget to back up any important data before performing a factory reset.)
To perform a hard reset follow this easy steps
1) Power on your phone.
2) Press volume up button + home button + search button at the same time for 5 seconds
(see the image below for the buttons location)
3) A message will appear " Are you sure you want to factory reset?"
5) Press yes and wait for phone to restart.
6) You've done resetting your GT540.