As PowerShell becomes more important, you may want to automatically check whether it is available on a machine. To determine whether any PowerShell version is available, check whether this key is available: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PowerShell\1
You could do that from within PowerShell, too, but you won't be able to run it if PowerShell isn't available:
Test-Path registry::HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PowerShell\1
