[sector24]

Fallout 3 checks for certain types of software on your machine before it lets you play. In particular you cannot have programs like Daemon tools or any kind of CD burning/ripping software, or anything like that. This is basically another unsuccessful anti-pirate tactic that penalizes legitimate consumers. The double barreled shotgun of irony is that a torrent of the game is widely available.

So the solution to your problem is to uninstall the offending software, whatever it is.