BioShock was criticized for its use of the SecuROM copy protection scheme, which limited users to only two "activations" of the game; while 2K responded by increasing the number of activations per game to five, much of the negative reaction to the limit remained, leading 2K to promise a tool that would essentially cancel an activation on a single machine, making it available for use in the future.
The tool works only with the retail release version of BioShock, as the Steam version of the game automatically cancels an activation when the game is uninstalled. The tool does not work with the Direct2Drive release.
There are limitations to the tool's effectiveness: According to the FAQ, the revoked activations are valid only on the computer on which the game was originally installed, and only as long as no "major hardware component, such as a motherboard, hard disc drive or DVD ROM" has been changed. Further, the tool will only revoke one activation per computer, regardless of how many individual copies of BioShock have been installed.