============
Windows 7 or Later
===
PowerShell -NoExit "HelloWorld.ps1"
Note: -NoExit is not needed to run the file, but without it, the PowerShell window would close too quickly to read the "Hello World!"
You may need to enable execution of PowerShell Scripts, as Windows blocks them by default. Run Set-ExecutionPolicy unrestricted in PowerShell as Administrator to allow this.