const
 pszLog = 'SYSTEM\CurrentControlSet\Services\EventLog\Application\';
begin
 with TRegistry.Create(KEY_WRITE) do
  try
   RootKey := HKEY_LOCAL_MACHINE;
   {Event log}
   if OpenKey(pszLog + Name,True) then
    begin
     WriteString('EventMessageFile',ParamStr(0));
     WriteInteger('TypesSupported',EVENTLOG_ERROR_TYPE);
     CloseKey;
    end;
   {Description under Windows 2000 and higher}
   if Win32MajorVersion >= 5 then
    if OpenKey('System\CurrentControlSet\Services\' + Name,False) then
     begin
      WriteString('Description','your description');
      CloseKey;
     end;
  finally
   Free;
  end;
end;