The operating system is used extensively on the International Space Station has been Windows XP. On the other hand the majority of the ground-based support systems for the ISS back on Earth are Linux-based.
Soon, the dozens of laptops in use on the ISS will all be running Debian 6. According to Keith Chuvala, a United Space Alliance contractor, manager of Space Operations Computing (SpOC) for NASA, and leader of the ISS’s Laptops and Network Integration Teams: “We migrated key functions from Windows to Linux because we needed an operating system that was stable and reliable – one that would give us in-house control. So if we needed to patch, adjust or adapt, we could.”