So I was just browsing through my CCs using the CC Magic, and found out that I have several files Sims3Pack files which appears in the "Defaults pre-installed set" of the program, but did not appear in my game or launcher. I don't have the .sims3pack files anymore, so I can't try to manually re-install them. Anyone knows how I can force them to show up? thanks

Did you install the items using CC Magic or the Launcher?

The launcher, but I think they got uninstalled when I deleted the Downloads folder from My Documents (a stupid move, but too late to fix that). Still, the CC magic still considered the items "installed" and I'm wondering if the CC Magic could somehow be used to retrieve those stuffs.

You'd be better off asking Grant himself, at his forum, or the download thread.

It should be safe to delete the sims3packs from downloads folder, it doesn't remove installed cc from the game, only from downloads in launcher. Installed contents are saved as package files in th DCCache (or in Library), and also a copy of the package files are saved in DCBackup (but the game doesnt use the backup). As far as I know it is only if you empty DCCAche or Library it should remove the contents from the game.

Ah, never mind. I just replaced my hard disk (the old one got smashed), and lost all my data, anyway, so I suppose it doesn't matter. Pity about the stuffs, though

Sorry to hear that.
But, may have been a blessing in disguise? Now, you can re-organize CC... Game Help:TS3 Organizing Custom Content^wiki