Over the last few years, there have been add-on programs created for The Sims - all of them free. You'll need a program to organize your downloads, create your own wallpaper and objects, and delete corrupt files.
SimEnhancer is a nifty little program that allows you to change just about any of your Sims' attributes, including default clothing, relationships, and job.
If you are addicted to downloading objects for "The Sims," you need this program. It allows you to categorize your downloads for "Hot Date" and "Vacation," and put your objects in .far files.
EliSims is neighborhood manager, allowing you to easily switch neighborhoods. This is especially useful for those who do not have either of the expansion packs. You can even back up neighborhoods with EliSims.
If you download a lot of user creations for The Sims, you'll need this program. It will search through your files, and clean up the damage or incomplete files. Game crashes are often caused by damaged files. One of the major offenders is skins, so be sure to have this program handy.
If you want to create your own wallpaper and floors you'll need to download this program. You need to create the wallpaper in a paint shop program, import the file into HomeCrafter, and export into the game. You can also test out what the wallpaper and floors will look like in a game.
So you've been downloading other's creations for a long time now, and you want to create your own. The Sims Transmogrifier is the program you need to download. This is a relatively easy program to learn. There is a tutorial on the official site that is very useful.