If you really want to flash nokia asha 303 here you can download latest updated flash files of this model. Some times your mobile hanging with the reason of many functions at a time. So it is really important to flash or reset factory of your mobile with its latest flash files. First of all you will need to download latest flash files of your mobile then flash with micro box. If you haven't micro flashing box you can flash your all those nokia mobiles which can support for usb data cable you can flash it flashing software phoenix service.
Note: Before flashing please don't forget to take backup of your important data like images,contacts,messages and all those data which stored in your phone. Because after flashing your will lose your all of data and your mobiles will restored in its original settings.
After succesfull completing of flashing your mobile will restarted manually.
Now you can download latest flash files of your mobile: