Sims 3 doesn't work after installing expension pack

Hi everyone.

I've played sims 3 with expensions for months now. Yesterday I tried to install another expension ( from games4theworld ) but after that the launcher didn't work anymore and i could open it any other way. I deleted the expension i installed but after that sims still didn't work. I've tried everything, including delete and install everything again. After that I could open the game but he couldn't find the expensions. I tried to start the game up again but then the launcher didn't work again. I tried to delete everything again but that didn't work.. I ended up resetting my whole laptop.. Now i want to downlaod it again but i'm afraid that the same will happen again. Can anyone help me with this?

Also,

Some of the instuctions say that you have to have the base game from games4theworld to download the expension but i've bought the game. Can I still install them?

Thanks!!

Okay I downlaoded sims 3, and it worked. Then I installed an expension and now sims launcher doesn't work.. Again..