procedure ShowPageConstantName(PageID: Integer);
var
  S: string;
begin
  case PageID of
    wpWelcome: S := 'wpWelcome';
    wpLicense: S := 'wpLicense';
    wpPassword: S := 'wpPassword';
    wpInfoBefore: S := 'wpInfoBefore';
    wpUserInfo: S := 'wpUserInfo';
    wpSelectDir: S := 'wpSelectDir';
    wpSelectComponents: S := 'wpSelectComponents';
    wpSelectProgramGroup: S := 'wpSelectProgramGroup';
    wpSelectTasks: S := 'wpSelectTasks';
    wpReady: S := 'wpReady';
    wpPreparing: S := 'wpPreparing';
    wpInstalling: S := 'wpInstalling';
    wpInfoAfter: S := 'wpInfoAfter';
    wpFinished: S := 'wpFinished';
  else
    S := 'Unknown or custom page ID';
  end;
  MsgBox(S, mbInformation, MB_OK);
end;