Samsung S3 i9300 restart on samsung logo and not going in download mode or recvery mode... i give u solution. i tested in many sets....
switch off ur mobile and then plug usb in and connect ur set with pc ,
then use volume up + home + power for recover mode.
now ur in recovery mode option then select wipe data,
now restart ur set.... now ur set 100000% ok
i teste in many sets...its working well....... so enjoy frnds