Max Trinidad walks us through an issue with Powershell Core Preview 3:
Just in case you haven’t try to install PowerShell Core Preview.3, in Windows, which became available on the evening of the 10th of December. If are doing a clean installation, meaning that it was previously manually uninstall, or that this is your first installation, then you are fine.
The issue with installing PowerShell Core Preview.3 is when you do an upgrade over a previous version: either Preview.1 or Preview.2.
That’s a common occupational hazard when working with preview tools. But Max has your solution.