re-installing 4.2.1 to orignal state after breaking fail

Read last line for what i want to achieve*, below is the problems and things i did to try to get unity to the same state when i first installed it, ty

Just starting out doing some tutorials, i decided to get familiar with the program by just playing around, i went to delete a object i had in my scene not realising i was still on "All prefab" in the favorites under projects tab, i also was mucking around with the skybox prefab, i reset the skybox component (c what happened) now the prefab 4 skybox is saved to the reset, i can get the texture back in but it just doesn't look(behave) the same.
All that said, i uninstalled, followed the forums removing from my regestory (regedit) removed every reference (find next..function) which showed me more places on my drive unity had gone then the forums said it would.
Installed 4.2.1 again. Still broken, getting errors what weren't there before.
All i want is to have it the same as when i first installed.
6hours later no luck, unity runs but with errors no "all prefab" in projects tab" and skybox prefab shaders broken

*Have unity 4.2.1 same as when i first installed.