Hi Glitzy,
that is a new phenomena that has been going on since the FL patch. It seems to be getting worse. There are a new kind of files (I don't know if they were originally package or Sims3packs files, could be package files that someone has converted but I think it's actually both) that seemed to be inside the package file of the Sim itself. One will need to delete the Sim to get rid of the download.
They do show in Custard. It looks like this:
http://4.bp.blogspot.com/_xvORAW5dL9U/TQKFTK8Xc3I/AAAAAAAABH4/6vptrMV43xk/s1600/SimMitAnhaengsel.jpg "width=600"
Note the hair reference in the SubType. If that shows, the Sim has the hair. You won't find it in the launcher and it will show in CAS with the little package-file folder. I find this a huge problem but as always, no one cares.
So I try to educate people to uninstall it and I'll probably do a wiki entry at MTS about it, just have not found the time yet (done one with pics in my blog).
Best is, not to install such a sim in the first place.
Some of the bad ones seem to be ingame like this too.
