DLL HELP!!!

Hi there.

Im struggling with a project that includes a dll, so i got an example off the net that shud run quite simply but it does not, here is the source code and the error.

I dont know if it could be my system configeration?

thanx.

class ShowMsgBox
  {
      public static void main(String args[])
      {
        MessageBox(0, "It worked!",
                  "This is a message box from Java", 0);
            }

     /** @dll.import("USER32") */
     private static native int MessageBox(
                                           int hwnd
                                         , String text
                                         , String title
                                         , int style
                                         );
  }


ERROR:

>java ShowMsgBox
Exception in thread "main" java.lang.UnsatisfiedLinkError: ShowMsgBox.MessageBox(ILjava/lang/String;Ljava/lang/String;I)I
      at ShowMsgBox.MessageBox(Native Method)
      at ShowMsgBox.main(ShowMsgBox.java:5)
>Exit code: 1