I've been playing the sims for about a year, but I only just discovered the exchange. Lately I've downloaded and installed a couple worlds, but when I tried to play on one of them they don't even show up for me to play on! I've tried a couple other threads, but all of them give me the same advice, "see if you can uninstall it from the launcher, and if you can't....blah blah blah,". I can uninstall it though. HELP!!!!!!!

How did you install the worlds from the Exchange? Did you click "save file" or "add to game"? If you clicked save file, you must manually install the world into your game. If you choose "add to game" did you get the launcher with the game listed? Sometimes you have to click on "install" at the bottom of the launcher. To check to see if the world is installed, in Windows, look in My Documents/Electronic Arts/The Sims 3/Installed Worlds. If the world is not listed there it did not install correctly. Sometimes worlds that require expansion packs you don't have won't install or won't play. Lastly, once the game launched, did you click on the + for "New Game"? Sorry if this is too basic, but it's hard to tell from your post how you installed the worlds.