I have my own method. This requires hidden files to be viewable under folder options.
C:\Documents and Settings\(user name that Spore is installed under)\Application Data\SecuROM
Delete the SecuROM folder and you're done.
That won't un-authorize your machine.
That might simply just cause you problems if the game tries to re-authenticate, or future authentications, nothing more.
Authorization requires internet activity because it sends to EA your machine's Authentication code.
So as long as EA still has that authentication code in their system, that's -1 install for you.