Microsoft is releasing a lighter version of Windows 10 for Redstone 5, the big OS update due out in the Fall. Dubbed "Windows 10 Lean," it features an installer 2GB smaller than Windows 10 Pro and loses basics such as wallpaper, drivers for CD/DVD drives, and apps like Regedit. It is not clear what Microsoft plans to do with the SKU. It may simply be intended for virtual machines, or Microsoft may be looking to make another go at a version of Windows for really low-powered devices.