diff --git a/src/ClaudeMailbox/Cli/ServiceCommands.cs b/src/ClaudeMailbox/Cli/ServiceCommands.cs
index b6856cc..8a70bdf 100644
--- a/src/ClaudeMailbox/Cli/ServiceCommands.cs
+++ b/src/ClaudeMailbox/Cli/ServiceCommands.cs
@@ -92,7 +92,10 @@ public static class ServiceCommands
             "obj=", "NT AUTHORITY\\LocalService");
         if (createExit != 0)
         {
-            Console.Error.WriteLine($"sc create failed (exit {createExit}).");
+            if (createExit == 1073)
+                Console.Error.WriteLine($"Service '{ServiceName}' already exists. Run 'claude-mailbox uninstall-service' first.");
+            else
+                Console.Error.WriteLine($"sc create failed (exit {createExit}).");
             return createExit;
         }