Hello, welcome to the forum,
Which version of Captivate do you use? I think you will have to delete the Preferences to clear up what is showed in the lists, only deleting the files in the Gallery will not be sufficient. What you have to delete depends on the Operating System (for the path) you are using and on the Captivate version.
It is Captivate5 on WinXP-32Bit.
I can not find any INI File or Reg-Key for this.
It is not an INI-file nor a reg-key, you will have to delete the folder Captivate in your profile, Appdata\local\Adobe. And you will lose all customisation. Sorry that I cannot give you the exact path (hope someone else pops in) because I'm on a Win7 laptop for the moment and the path is different in XP.
Now I am happy again. Thank you!