In case you forgot Google details, you might need to Factory Reset the phone. To do this, power off the phone and then pull out the battery for a few seconds. Put it back and press Volume Down + Power/Lock key until the Android logo appears. Use volume buttons to select and choose Wipe Data / Factory Reset and press Home button to confirm then reboot the phone using the same menu.
Wait a few seconds and your phone will be restored to factory defaults removing the lock and any additional applications installed or settings configured.
