If you have not arrived here as part of it, or if you are not 100% sure it's a downloaded file that is causing the problem, please go and read that FAQ first, and it will lead you back here if you need to do this. This FAQ is meant to be read as part of a step of the Game Problem FAQ. There are many tools you can use for scanning your files, such as SimPE or The Clean Installer, but this method will show you a way of finding a problem file quite quickly without using any of these. If you have put everything you've downloaded into your Downloads folder without categorizing them into subfolders, it can be tricky to figure out which file is causing the problem when your game is acting strangely. But the trouble is, you have thousands of files in there, how can you find out which one is the problem? You've read the Game Problem FAQ and you've removed your downloads or saved sims folder, and you know the problem is in there.
Maybe it's crashing, or perhaps it's not working quite as it should.
You're playing the game, or running bodyshop, and something strange is happening.