Powershell window preventing shutdown

Question

If I have a PowerShell window (at the PS command prompt) on display it prevents the computer shutting down.

i.e. if I open a powershell window and then try to shutdown the server, I get the End Program popup saying Windows cannot end this program

I get the same result if I start the powershell from the start menu, from a cmd prompt and from a shortcut with -NoExit specified.

Any ideas how I can get shutdown to automatically close a powershell window (if it is at the PS prompt) in the same way as it would for a CMD window?

Alternatively, is it possible for PowerShell to detect when a shutdown has been initiated and therefore close itself?

Update:

Going down the alternative route as suggested by pk. I have come up with this test code:

Write-Host "PowerShellBlockingShutdown.ps1 Started"

$global:shuttingDown = $false
$sysevent = [microsoft.win32.systemevents]
Register-ObjectEvent -InputObject $sysevent -EventName "SessionEnding" -Action {$global:shuttingDown = $true; Write-Host "  SessionEnding"} 
Register-ObjectEvent -InputObject $sysevent -EventName "SessionEnded"  -Action {$global:shuttingDown = $true; Write-Host "  SessionEnded"} 

do {
    Start-Sleep -Seconds 3
    if ($global:shuttingDown) {break}
    Write-Host "  Waiting for Shutdown"
} while ($true)

Write-Host "PowerShellBlockingShutdown.ps1 Finished"

Which seems to work

Answer 1

I'm blatantly cut/pasting this answer from another site (since linking is frowned upon and I don't have a better answer). I do believe this will resolve your problem.

...it looks like you can set up a Event watcher using Register-ObjectEvent using [microsoft.win32.systemevents] and watching for either SessionEnding or SessionEnded. I haven't had time to test this out, but you could look at using something like this:

$sysevent = [microsoft.win32.systemevents]
Register-ObjectEvent -InputObject $sysevent -EventName "SessionEnding" -Action {"Shutdown/Logoff detected.";Get-Process -Name Powershell | Stop-Process -Force}

More information about this class can be found here: http://msdn.microsoft.com/en-us/library/microsoft.win32.systemevents_events.aspx