I tried to use a .blend file that is 1 year old. I wanted to use the mesh to animate something, but I noticed I used EdgeSplit instead of auto-smoothing a year ago. Here is the problem, when I "remove doubles" and turn on auto-smooth nothing happens. Is the file corrupted, does Blender doesn't support older .blend files? Please help, I literally sat 3 hours here pressing random buttons like a monkey and nothing seems to work <3
Apparently Auto Smooth wont work if you have custom split normals, if you want to use it you will have to remove any custom normals and loose it's data.
In the Properties Window > Object Data (Mesh tab) > Geometry Data Panel > Clear Custom Split Normals Data button and you should be able to use Auto Smooth
Otherwise just add an Edge Split Modifier