Set PowerShell ISE as the Default Program for Opening PowerShell Scripts

If you want to set PowerShell ISE as the default application for opening PowerShell script files (.ps1), you simple need to change the file type associations on the local machine.

Open Control Panel > Programs > Default Programs > Associate a file type or protocol with a program. Navigate to the .ps1 file extension and select it.  Click Change Program and navigate to the PowerShell ISE executable, which is located at C:\Windows\System32\WindowsPowerShell\v1.0\powershell_ise.exe.  The change is saved automatically after selecting the application.