Microsoft's stripped-down Windows will be called Windows 10X and not Windows Core OS as we previously thought.
The new version of the Windows operating system is thought to be appearing on the Surface dual-screen device, codenamed Centaurus. The Windows 10 X name has leaked ahead of Wednesday's Microsoft Surface launch.
It appears the OS is intended for use on foldable or dual-screen devices, using apps from the Windows Store or other apps in 'containers' or under emulation in other words.
However, it's unclear why the OS might only be for foldable or dual-screen PCs. The Chrome OS rival may also appear on other third-party devices after that as Microsoft seeks to appeal to those looking for lighter, less intensive operating systems - aka would-be Chromebook or iPad buyers.
As with the failed Windows 10 S and Windows RT before it, we're concerned that once again Microsoft won't succeed in explaining the difference between its lighter operating system and full-fat Windows 10.
We don't know if the new OS will run full desktop apps or not (as we said above they may be run under emulation) but if not, Microsoft will need to inform consumers.
We're also expecting a new Surface Pro 7, Surface Laptop 3 and an ARM-based Surface called Surface Campus to debut at the event.
We're now not expecting a new Surface Book 3 tomorrow - this may see the light of day next year.