I worked on a neighborhood for 3 months and now it won't install
I place it (From exports) into my downloads folder and open the launcher but it says its already installed. Its not!
I tried making a new hood and installing it and it worked...
Please help!

I had the same problem
1) If you want to remove the old world uninstall it through the game luancher
If you manualy deleted the files then I suggest uninstalling and reinstalling all your som programs. Install Highend last, otherwise the world editor will not work
2) Change the world discription on the world editor. Make sure you give the world a new name.

Before exporting make sure all the routing is good. Do this through the show routing option. Use the wire frame option to double check bridges, stone, etc. If a sim can not rout to a location you game will freeze.

Be warry of download other people lots, people tend to use too many plants, I think no more then 4 plant types alot, double check the world builder manual.

Before installing extra content, include EA stuff, finish your world. The world builder ingame editor sticks on new content.

apart from uninstalling using the launcher, you also need to go into world caches and delete any of them that beliong to your old world, it's likely to be this more than anything, if you delete the world caches after uninstalling with the launcher, you don't even have to rename your world or change the description