The only reason that XP would be unsupported would be if DirectX 10 is used as a base graphics API. This is not very common, but it has happened (Battlefield 3, Just Cause 2, etc.).In my opinion, the graphics don't look good enough to use DirectX 10 as a base, but that's a total guess. The 60 frames per second leads me to believe it will be based off of 9, which might comfort some people. Lets hope for an official statement soon. Also, it is correct that Steam refunds preorders as long as the game isn't released yet, right?