开发的一个程序，使用sql2005企业版正常，但在别的机器上安装的express版连接失败。该如何解决

        HRESULT hr = m_conn.CreateInstance(__uuidof(Connection));
        if( FAILED(hr)) 
        {
            CString sMsg; sMsg.Format("CreateInstance失败,0x%u",hr);
            TRACE("数据库连接失败！%s\r\n",sMsg);
            throw sMsg;
        }
        CString conn = "Provider=SQLOLEDB;Server=127.0.0.1;Database=db_test;uid=sa;pwd=sa;";
        if(FAILED(m_conn->Open((_bstr_t)conn,"","",-1)))