Allow displaying a boot message

scripts/Windows/Scripts/Registry.ps1

@@ -16,4 +16,33 @@ $null = New-Module {
         [System.GC]::Collect();
         & reg unload $regRootPath;
     }
+
+    <#
+        .SYNOPSIS
+        Sets a message to show on the login screen.
+
+        .PARAMETER Caption
+        The title of the message.
+
+        .PARAMETER Message
+        The text of the message.
+    #>
+    function Set-BootMessage {
+        param(
+            [string] $Caption,
+            [string] $Message
+        )
+
+        $options = @{
+            legalnoticecaption = $Caption;
+            legalnoticetext = $Message;
+        };
+
+        foreach ($key in $options.Keys) {
+            Set-ItemProperty "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System" `
+                -Name $key `
+                -Type "String"
+                -Value ($options[$key]);
+        }
+    }
 }