Installing Forza 3's second disc, essential if you're going to get the game's full experience, takes around four minutes: watch the video after the break as proof.
The extra DVD contains 1.9Gb of data, such as car packs, tracks and environments.
If you don't have enough space on your 360's drive, the game asks you which car packs you want to install. You won't see that in this movie as we'd cleared out a bunch of stuff beforehand.
Look and see. This was grabbed from the retail version, which releases on October 23.