Move the old one back into Documents\Electronic Arts, and use the launcher to uninstall all the store worlds that haven't been working. Trash the new Sims 3 folder you've created, the one into which you've been installing store worlds. The instructions are mostly the same, with an extra step, so I'm going to add that and just c/p the rest of the instructions, while (hopefully) changing all the tiny details that matter.
Information, Guides and Announcements for the EA app.
