We already knew Microsoft was at least toying around with putting Windows on the OLPC XO, but it looks like things have just gotten quite a bit more serious, with the OLPC folks now saying that they're working "very closely" with Microsoft to develop a dual-boot Windows / Linux system for the laptop. What's more, Nick Neg himself reportedly said that the version of Windows that's now up and running on the XO is "very fast" and "very, very successful." There's no word just yet as to when we might actually see such a system be released, however, but OLPC is apparently now talking with Microsoft and "possibly" the Bill & Melinda Gates Foundation about putting the XO to use in some of the education programs Microsoft runs in developing countries, a possibility that Negroponte says is "really cooking at the moment."