//
 //只能运行一个实例
 HANDLE hMutexOneInstantance=CreateMutex(NULL,TRUE,_T("PreventSecondInstance"));
 BOOL bFound=FALSE;
 if(GetLastError()==ERROR_ALREADY_EXISTS)
  bFound=TRUE;
 if(hMutexOneInstantance)
  ReleaseMutex(hMutexOneInstantance);
 if (bFound==TRUE)
 {
  //::AfxMessageBox("您已经运行了一个实例");
  return false;
 }