Let me write again a tutorial on a Samsung device. And this one is for Samsung Galaxy S Duos S7562.
Hard resetting / factory resetting your phone will solve the following issues:
1. If you forgot your pattern lock 2. If you forgot your gmail account 3. If you forgot your password 4. Apps that automatically force closing 5. Stuck in Samsung Logo (sometimes does not work if the firmware is totally damage)
NOTE: Performing hard reset will erase your data.
To hard reset:
1. Turn off your phone. 2. Press and Hold VOLUME UP + VOLUME DOWN + HOME Button + Power button. Keep pressing and holding until the phone power up, release only the power button when it power up and wait until you enter in Android System Recovery.
3. Select wipe data / factory reset. To navigate press the VOLUME ROCKER, to confirm your selection PRESS POWER Button 4. Reboot your phone.
Note: If performing hard reset did not succeed, you need to wipe the cache first in the android system recovery before performing wipe / factory reset.
I hope this tutorial helps you.. If you have any question just drop a comment.