Re: What do I have to do to fully reinstall Spore? Am I missing a step?

Update: I found a solution!

1. First, uninstall Spore like you did - Delete all InstallShield Installation Information, its registry entries, and game files.
2. Next, restart Origin (so that it refreshes its cache)
3. After that, install Spore in the order of Base Game, Creepy and Cute Parts Pack and followed by Galactic Adventures. At any point, do not open the game.
4. Once all the components are installed, you can open the game and it should prompt you that "a new patch is available". Simply click "Yes" and "Install".
   You have to be logged in to spore.com to be able to see the "There's a new patch" dialog.
5. Spore should close itself, and the installer should update you to Patch 5, and Patch 1 for Galactic Adventures.

Now, you can start playing Spore as per normal.

As for why the installer was installing it all at once: It was because you have all two DLC's purchased.