Already revealed by SEGA's Universe at War Live compatibility on Vista/XP, Microsoft's official Gamerscore blog confirms it is indeed working on bringing the Games for Windows Live service to XP. The development team first wanted to get the service working on Microsoft's newest OS to support Halo 2 and Shadowrun, but now that both titles are out, work on finalizing GfWL on XP has commenced. Gears of War, which is Vista/XP compatible, will support the Live service on both platforms.