The phone start nicely as the power button pressed.But after showing the windows logo when starting,the whole screen goes blue and nothing happended then.Please i need to flash the rom and insert a custom rom into it so that i can use this as before.
BIOS?? Custom rom? We don't have either for the 640. You could unlock the bootloader and then flash a similar 'image' to the phone, but you'll need to be on xda for that