Flash with official rom

link

http://www.4shared.com/rar/QyJGIF8J/odin_185.html

you need to download i9300 official firmware version 4.1.2

  Link

http://terafile.co/6c4717b9391c/I9300XXEMF6_I9300OLBEMF3_XXV.zip

extact this file

and then

First shut down your device, then power on by simultaneously pressing the power button, home button and volume down key. Now you will see download mode and you will be asked if you want to cancel or continue. Press volume up to continue or volume down to cancel and reboot.

select PDA

plug ur usb

the drivers will detect

it shows com port

like as this pic

after that

click start button in odin

finally its flashing is finised

after this mobile is upgrading after that

pls remove ur battery and put again

try hardreset

combination of the keys is

Turn the phone off.

Press and hold VOLUME UP and Home(center) button

Press Power until the phone vibrate

Wait until you see the Android logo then release all the buttons.

Select Wipe data/Factory reset with VOLUME DOWN, press Power (right hand-side)

Select YES -- delete all user data with VOLUME DOWN and then press Power

After format, press Power again to reboot phone. (select reboot system now)