Deleting from the Launcher removes it from your game, but it won't give you your disk space back.
![Tongue](/smf/Smileys/default/tongue.gif)
Take the Sims3Packs you downloaded and put the ones you don't want aside. Then delete your DCCache folder. Then reinstall the downloads you want to keep. Because it is such a hassle, it's best to avoid installing anything with the Launcher unless you are completely certain you want it. To test something new in-game, back up your DCCache folder before installation to make the process less painful.