User blog comment:Lost Labyrinth/Tips on improving the visual quality of TS3 with minimal performance impact/@comment-24611888-20140301145149/@comment-2201555-20140301203119

If you read my instructions properly, and I would say that they are clear, then you would know that you're supposed to put the d3d9.dll from injectSMAA into *INSTALL DIRECTORY*/The Sims 3/Game/Bin with everything else. I don't know where you got the idea from that you're supposed to install this in your system directory.

What you did will probably hurt your OS. I strongly suggest you undo that change. Note that the sfc (System File Checker) command will not fix it for you, so if you didn't bother backing up the system-wide d3d9.dll then you're only hope is to fully reinstall DirectX, and failing that, reinstalling Windows.