I tried to install sims 4 on Origin last night, and had it installing through the night. After it had finished installing, I suddenly get an install failed error.
I don't mind starting it over, but on top of it not installing, it still took all the memory it needed to install. How can I properly remove all the files so I can start again, without damaging any files?

windows? 10? start by clearing out your storage in settings. uninstall sims 4 - and the files would be under Program Files on your c: drive in the Origin Games file, if you have not completed an install and you want to delete the folder prior to re-install. Under origin application settings you can save the installers so you don't have to download again - until you have successfully installed and run the game, then you can delete. Clear your internet cache and only download the base game. Install and run only the base game. Everything good? then add your expansions/packs, clearing your cache and storage frequently if need be. You may also need to google a solution regarding memory and the game - but does your pc/laptop have the specs required to run it? What about stopping background processes that you don't need?

Make sure your windows and drivers (nvidia/intel) is/are updated as well. When I first got my laptop (gaming) the game kept crashing until windows updated to a point (?!*#$&^%). This doesn't point to the original issue you have, but can save you further frustration if need be. There is not a lot of info in your post, so I may be filling blanks incorrectly. I have had my share of frustration with installing on different windows systems and different laptops and pcs.

You may need to lower the gameplay settings once you are in game.