I play cracked, so for me its install and go. But I believe the game uses Steam to install itself, so you can probably play without a disc.
The game is only a baffling 5Gb... how they did it beats me, but it sure saved me precious download time!
@Arch: I haven't even fought a dragon yet, as soon as the game gave me full control I got distracted by shiny things on the horizon and I kinda got lost after that. Fuck Spriggans.