"Game isn't installed correctly" when trying to start the game

I've been getting this message when trying to start the sims 2 for a few days, all of a sudden. "The Sims 2 isn't installed correctly. Please install or reinstall." Before that everything worked fine. I only downloaded a bit of CC that day. I already testet the cache files, the new CC, reinstalled the base game and EP9 but it still won't start.
I have all EPs, play on Disk with Windows 8
Can somebody help?