exactly what do you do when you download them?
Here's an "user manual" for you:(0. open the zip/rar file, and take the
.package OR the
sims2pack files out of the folder)
1. open the
sims2pack files with
sims2pack clean installer (the default maxis installer is buggy at best)
2. click install (the files will save themselves in the downloads folder)
3. if you have nightlife or newer expansion packs (EP), you can make folders - so I'd make one folder for each sim if I were you, with pictures of the sim inside. It makes it easier to remove the sim or make-up and such if you don't want it anymore.
4. make sure you also download meshes, and make sure you know what is included with the download (some put on maxis clothing/hair when they package the sims)
5. open CAS
6. find sim
7. use it as it is, or modify it to your liking.
8. if they still won't show up -
did you remember to enable custom content and then
restart the game?
9. are you sure you have the expansion/stuff packs required for the sim to work?
hope this helps.
and remember that there's a "game help section" here at insim.