When migrating an ATL project from vc6 to vc8, you will get a problem about CComModule. Problem: In vc6, there is such a declaration in stdafx.h as: extern CComModule _Module; and in the main module: CComModule _Module; But when you complie it in vc8, the following errors apears: c:\temp\myatl\stdafx.h(24) : error C2146: syntax error :