Windows XP is garbage and nobody with a modern PC would run it when Windows 7 runs circles around it in every aspect. While Microsoft may still support XP, and very lightly they support it, developers don't. Why would a developer develop software for a out dated OS?
Any PC gamer today is running Windows 7 64bit. PC parts are cheap, upgrade, it's worth it.
As far as Steam sending you a real tone cable, if it's included with the purchase I'm sure they will. They send you out the items for other game titles.