My best suggestion is to use Delphy's download organiser that can be found at the MTS2 site.
You can find orphan files, duplicates, sort your downloads by type, move them to other folder and delete all in the same tool.
It is a must for people with a lot of downloads.

Once you got rid of the duplicates and orphan and sort them by type in subfolders, you can also use the Clean installer which will give you a preview pic of some of the downloads you have. It is also a good tool to install downloads since it will give a detailed list of the stuff you are about to install.
No tool can tell you if you are actually using any of the cc shown.
If the preview pics does not help, the best is to go in game and delete them manually.
One last thing, once you are done cleaning up your downloads, delete groups.cache file and cigen.package file. Both will be regenerated the next time you start the game or Bodyshop. They can both be found in your c:/mydocuments/eagames/thesims2 folder.
Note that you will have a cigen.package file only if you used bodyshop before.