Pets Uninstalled? What?

Ok, after I was bored with TS3, I wanted to go back to TS2 so I loaded up the game. After the game took more time to load than usual, I get a message saying that Pets has been uninstalled and playing a neighborhood will delete all the pets. I clicked the exit button and checked to see if Pets really was uninstalled, but the files appeared both under Program Files> EA Games>TS2 and under the Add and Remove program. Another thing, some of the neighborhoods I previously deleted, like Deserate (sp?) Valley, popped back up in the Neighborhood folders with folder names like E001 and G001.

I don't understand what happened, I never messed with anything nor have I uninstalled anything. I can't remember the last time I played, but I do remember not doing anything more than just check on a family. Does anyone have any ideas what in the world
happened?

Update: I decided to uninstall pets and reinstall it. Everything seems to be working now...