Alienware m11x laptop, but I was about to lose my cool this morning because I could not get Bioshock to run via Steam. I was getting the dreaded "This game is currently unavailable" error message when launching the game.
Steam support has a great guide for this problem. Unfortunately, the step I needed to take was towards the bottom and it took me a long time to get to it. I first did the Windows 7 troubleshooting, then driver updates (which are not easy on the m11x thanks to Dell's m11x vs. m11xR2 branding), and then I ran every option on the list; except for one that I didn't think was needed: Verifying Game Cache Files (GCF)
It took a few minutes to verify Bioshock's files and in the end it found 5 missing files. A few seconds later Steam downloaded the missing files and Bioshock now works. So, lesson learned. Do the simple steps first and then worry about going ape shit with deleting/reinstalling/etc.