Running a Sims 3 expansion without the CD?

I own, and have installed, the Sims 3 World Adventures, and Ambitions. The ambitions cd though has become scratched pretty bad, and I've browsed the cracks, but being not the most tech speak savvy, I'm unable to determine what I should download, that wont try to blow up my computer :) So my question, does anyone know of one? ^_^