I unchecked all of them and tried to start it, still didn't work.
What you mean with that. !!!! (What have you unchecked !!!)
I assume you haven't any mod's. !!!
Likely means unchecked all the DLC. I would try a clean reinstall.
from another thread:
First you need to uninstall Skyrim
This is how:
After its been removed there are folders you'll need to verify that they've been deleted.
There shouldn't be any Skyrim folder in "..\Steam\steamapps\common"
BACKUP FIRST (make a copy of it somewhere) then delete the Skyrim folder from "..\Documents\My Games\"
e.g. "C:\Users\
(This folder is where the game keeps its savegames)