The One Laptop Per Child project originally started out with its own custom Linux based operating system, but has now announced it will be pairing up with Microsoft (http://www.pcworld.com/businesscenter/article/145970/windows_coming_on_dualboot_olpc.html) to deliver Windows XP on the pint sized laptop. The move is somewhat controversial, though I'm sure MS is happy about getting children in the developing world using the ubiquitous OS. As XP is a bit big to fit on the integrated 1GB flash memory in the OLPC XO, it will come preloaded on a 2GB SD card during the trial period. The original Linux OS won't get the chop though, allowing users to dual boot the two operating sytems. The machines loaded with Windows will enter trials in June and should be available come August or September, which will basically make it very similar to other ultra portables that are currently around (MS has spent time developing custom drivers for the OLPC however).