i tried to load the level, but it had "rendering issues" and Le crash

well, i had an old dell desktop running an older version of minecraft (i dont know which version) and since ive upgraded to my laptop it has updated from there... now as it says it has rendering issues. the thing is, it was a pre release version of the save file and i dont know if thats an issue (more likely...)
What I expected to happen was...:
java would have recognized the older maps and automatically re render it

What actually happened was...:
le crash
Steps to Reproduce:
1. loaded save files back onto .minecraft saves
2. updated minecraft
3. attempted to load level