To Stephenyoh the link you've given, you added a bracket in the UR. So it's
http://help.ea.com/en/article/manual-uninstall-for-sims-2-expansion-and-stuff-packs/
It helped. Yes you got to uninstall the previous Sims 2 + EPs + SPs before installing the Ultimate Collection.
Also Bodyshop is in the Fun with Pets folder. Just saying, because it could be downloaded separately on another site but coming with addtional things not being safe at all for your comp.
Fo the black rectangle issue, I already had it on the previous version with the last SP installed and it's easy to fix : on a lot, go to graphic settings and set Shadow to medium, and save from this panel on the lot.
Other than this it was worth the wait of 1 hr to download, because I never purchased some SPs or packs not available in France. All seems to work fine for me, as object and clothes retexturist for the Sims 2, even SimPE. Got more to explore, but would report any possible issue on this forum if I find one.
I guess that after 31 July 2014, the right code for the Ultimate Collection would be the product code ? I got this, but let's hope I won't need it, except if I ever had to replace my computer and re-install all.