Unity Free to Unity Pro.. Risk data loss

I upgraded my Unity from Free to PRO. when I tried to open my file (which was originally created using Unity Free), a dialogue box appeared saying that I might lose some data. I thought there will be no changes? I thought it is okay to use lower versions in new the new version? Please. I really need your help. :frowning:

Normally, at least for me, I havn’t had any problems upgrading projects to pro, but just to be shure, just like DaveA said, you should make a copy to test on, if it doesn’t work, you still have all the files.

Hope this helps