[AC Question]

My mobile GT-I9300 using since one year, now the phone is not responding properly and many a times showing ' android process stoped'

[B. Diddy]

Welcome to Android Central! Try booting into Recovery Mode and wiping the cache partition, which won't erase any personal data: [Guide] Rebooting into Recovery Mode for the Galaxy S2, S3, and Tab2.

If that doesn't help, try unmounting your SD card (in Settings>Storage), removing it, and rebooting, since a corrupt card can cause various issues.