I haven't worked out all the details yet (nor quite how the Steam system works!), but the competition is open to anyone with a Steam account, which is free to register and you don't have to buy anything (just fill out your wishlist and complete some "tasks") ... BUT you do need to have a broadband Internet connection.
The prizes are:
- Grand prize: win EVERY game on Steam
- 50 x first prizes: 10 games on their wishlist
- 100 x second prizes: 5 games on their wishlist
- 1,000 x third prizes: a Valve Complete Pack