diff --git a/Main.cs b/Main.cs
index 663c729..cde3e3b 100644
--- a/Main.cs
+++ b/Main.cs
@@ -120,7 +120,7 @@ public void Append(IEnumerable<string> values)
   }
 }
 
-class CommandBuilder
+static class CommandBuilder
 {
   public static string Raw(string command)
   {
@@ -251,9 +251,12 @@ public static IEnumerable<string> WriteToFile(string path, IEnumerable<string> l
     return lines.SelectMany(line => WriteToFile(path, line));
   }
 
-  public static IEnumerable<string> SafeWriteToFile(string path, string content)
+  public static IEnumerable<string> SafeWriteToFile(string path, string content, Encoding encoding)
   {
-    byte[] bytes = Encoding.UTF8.GetBytes(content);
+    byte[] bytes = Enumerable.Concat(
+      encoding.GetPreamble(),
+      encoding.GetBytes(content)
+    ).ToArray();
 
     int chunkSize = 256 - 70;
     foreach (string base64 in Convert.ToBase64String(bytes).Chunk(chunkSize).Select(chars => new string(chars)))
diff --git a/modifier/Script.cs b/modifier/Script.cs
index ee77eb7..62c07fe 100644
--- a/modifier/Script.cs
+++ b/modifier/Script.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text;
 
 namespace Schneegans.Unattend;
 
@@ -24,6 +25,25 @@ public static IEnumerable<ScriptType> GetAllowedTypes(this ScriptPhase phase)
       _ => Enum.GetValues<ScriptType>(),
     };
   }
+
+  public static string FileExtension(this ScriptType type)
+  {
+    return '.' + type.ToString().ToLowerInvariant();
+  }
+
+  public static Encoding PreferredEncoding(this ScriptType type)
+  {
+    UnicodeEncoding utf16WithBom = new(bigEndian: false, byteOrderMark: true);
+    return type switch
+    {
+      ScriptType.Ps1 => Encoding.UTF8,
+      ScriptType.Cmd => Encoding.Latin1,
+      ScriptType.Reg => utf16WithBom,
+      ScriptType.Vbs => utf16WithBom,
+      ScriptType.Js => utf16WithBom,
+      _ => throw new NotImplementedException(),
+    };
+  }
 }
 
 public record class ScriptSettings(
@@ -39,6 +59,15 @@ public Script(string content, ScriptPhase phase, ScriptType type)
       throw new ConfigurationException($"Scripts in phase '{phase}' must not have type '{type}'.");
     }
 
+    if (phase == ScriptPhase.DefaultUser && type == ScriptType.Reg && !string.IsNullOrWhiteSpace(content))
+    {
+      string prefix = @"[HKEY_USERS\DefaultUser\";
+      if (!content.Contains(prefix, StringComparison.OrdinalIgnoreCase))
+      {
+        throw new ConfigurationException($"{type.FileExtension()} script '{content}' does not contain required key prefix '{prefix}'.");
+      }
+    }
+
     Content = content;
     Phase = phase;
     Type = type;
@@ -111,7 +140,7 @@ static string Clean(Script script)
 
     var appender = new CommandAppender(Document, NamespaceManager, CommandConfig.Specialize);
     appender.Append(
-      CommandBuilder.SafeWriteToFile(scriptId.FullName, Clean(script))
+      CommandBuilder.SafeWriteToFile(scriptId.FullName, Clean(script), script.Type.PreferredEncoding())
     );
   }