这篇文章的地址:http://www.csdn.net/expert/pam/book10_1.shtm
在最后调用ATL时
(2) 在按钮TEST的消息控制函数中加入如下的代码:             HRESULT hr;   
             ISimpleInterface* pIntf = NULL;
             hr = CoCreateInstance(CLSID_SimpleInterface, NULL, CLSCTX_SERVER , 
                               IID_ISimpleInterface, (void **)& pIntf);
             if(SUCCEEDED(hr))
             {
                  pIntf->Welcome();
                  pIntf->Release();             }
返回以下错误:
impleClientDlg.obj : error LNK2001: unresolved external symbol _CLSID_SimpleInterface
SimpleClientDlg.obj : error LNK2001: unresolved external symbol _IID_ISimpleInterface
Debug/SimpleClient.exe : fatal error LNK1120: 2 unresolved externals
Error executing link.exe.