2K Games used an anti-piracy scheme that allows a limited number of installs of Bioshock. But the method was not very successfull, so they deicided to put a deactivation tool on their website to deactivate the anti-piracy system and to provide unlimited number of installs for the user. Unfortunately the tool will not work for the owners of the Direct2Drive version. The Steam version does not require this tool because the games comes already activated and uninstalling the game automatically deactivates it.