Oh look. Another PC game with a pointlessly restrictive limit on the number of installs. Aren't these kind of stories just heart-warming?
Irate users on the forums of both publisher Atari and developer Starbreeze are complaining that Riddick: Assault on Dark Athena only allows you to install it on three machines. After that, sorry.
Atari's response? That if you use your three installs and need more, and have legitimate reasons for needing more, you need to contact their helpline. Just so you can install a game that you own.