One way to spend six hours

Step 1. Create a new file called stdafx.cpp.
Step 2. In that file, add one line: #include <stdafx.h>
Step 3. Debug for many, many hours.
Step 4. Change stdafx.cpp to this: #include "stdafx.h". Note that the compiler now stops assuming you meant the stdafx.h buried deep inside the MFC source.
Step 5. Go home and have a drink.