Originally Posted by slaWter
You need to activate it on Steam just like you would with a retail Steamworks game.
Then enter the demo code you got from the pre-order or Borderlands GOTY version and the demo will show up on your Library.
where is the key from the pre-order btw? i never got one from the pre-order on steam, i did register my key i got from borderlands goty, i have a friend i want to give my pre-order key