Back then, The company promised to deliver a tool that would allow the user to choose which installs were to be left in place and which were not.
The announcement goes as follows:
“By running the de-authorization tool, a machine"slot" will be freed up on the online Product Authorization server and can then be re-used by another machine.
You can de-authorize at any time, even without uninstalling Spore, and free up that machine authorization. If you re-launch Spore on the same machine, the game will attempt to re-authorize.
If you have not reached the machine limitation, the game will authorize and the machine will be re-authorized using up one of the five available machines.”
The tool is available here.