Unity Crashes on Start Up

I have had Unity for a while now and updated to unity 5.0.2 when it first came out. When I saw the update for 5.1.1 I installed it and when it finished downloading I accidently opened the old (for some reason not deleted) 5.0.2. When it loaded unity's blue startup screen came up and crashed into a white box that says, "Unity Editor has stopped working, A problem caused the program to stop working correctly, Windows will close the program and notify you if a solution is available."

I have tried uninstalling and reinstalling, downgrading back to the old version. Alt'ing into a new project, doing (Start > Run > "DXDIAG"), (Start > Run > "regedit") then deleting the entire unity tech and unity folder.

Please help me on this one and maybe some other people in the future.

• helpless Unity User (LushLight)