Microsoft unveils Windows 10 and new wearable 3-D gadget

Software to be released as free upgrade for existing '8.1' and '7' customers

Microsoft on Wednesday took the wraps off a new version of Windows - and a new wearable 3D gadget it calls the HoloLens.

The company showed the new headset, which lets users view and interact with three-dimensional images, at an event where it also revealed new features coming to the company's flagship operating software.