Chunk errors, probably corrupt world

Yesterday, i played minecraft. I was happy because i had just made a full enchanted diamond armor. My computer was too hot, and shut down for safety reason. Today i went back to the world what i played in yesterday, and it was really strange. Some chunks were completly different than before. I know that this isn't really a bug, because it couldn't happen if the world is saved normally. But i really want my world to be the same as before. What can i do?

EDIT: MCedit helped me