Samsung GT-i5510 hard reset
-Hold 5(T) and Power for 5-10 sec.
-Wait... for Android Recovery Menu
-Choose "Wipe Data/factory reset" with cursor arrows
-Confirm with "Shift" key
-Go to "Yes..." with cursor arrows
-Confirm with "Shift"
Choose reboot system with same method
Note: if any of these solution is not working use adb (Android debug bridge) shell to hard reset your GT-i5510 phone. Install sdk and enable USB debug. Go to cmd.exe or bash and use adb in tools folder.
Press and hold "W" on the QWERTY keyboard and press POWER buttons together. (if not working, see other method below)
Use this method to hard reset your Samsung Galaxy 551 Android phone: Enter *2767*3855#. Warning! All your data including contacts, messages etc. will be lost! Copy all your necessary data/Contacts/Messages etc. to SIM or make backup to your PC before full reset! Take out SIM card before full reset.
Settings > Privacy > Factory data reset: Reset your settings to the factory
Your device freezes or has fatal errors
If your device freezes or hangs, you may need to close programs or reset the device to regain functionality. If your
device is frozen and unresponsive, press and hold [Power/Lock key] for 8-10 seconds. The device will reboot automatically.
If this does not solve the problem, perform a factory data reset. In Idle mode, open the application list and select
Settings → Privacy → Factory data reset → Reset phone → Erase everything.
All comments are welcome! :)