I suggest first run a backup of the device information as explained here. Then perform a system repair using PC Companion or Bridge for MAC. The process will erase all internal memory.You might need to charge your device for about 1-2 hours before so the device has at least 80% battery. Switch off your phone and unplug from Pc (Hold volume up and power for around 10 seconds) Start PC Companion and select Support zone then Update my phone/tablet then in Blue Repair my phone/tablet and follow the on screen instructions - When prompted connect your phone still switched off holding volume down or back button - This should start the repair or reformat process. If you are using Windows 8/8.1 or a 64bit operating system then adjust the settings for PC Companion and run in compatibility mode and chose Windows 7 or XP. Keep us updated please.
