After updating no version of unity will load.

hi,

So to explain my current situation. I'm using Windows 10, updated to 5.5.0 from the previous version. after updating unity editor would hang for ever on the splash screen. I removed the project folders, performed a clean uninstall on unity and deleted the licence files. installed 5.4

after installing 5.4 the splash screen no longer appears, the Unity task appears in the task mangier but nothing happens.

opening in administrator does nothing

opening in and compatibility mode does nothing.