To hard reset the LG Optimus S select menu, settings, privacy, Factory data reset. To save the contacts to your SD card before doing the reset open contacts, select the menu button, import/export, and export the contacts to the SD card. The photos and contacts will be saved to the micro SD card.
After the reset is competed, you will need to import the contacts back from the SD card. Open contacts, menu, import/export, and import the contacts from SD card.