Excel Interop Save as is giving compatibility checker in excel 2007

Excel Interop Save as is giving compatibility checker in excel 2007

Here is my code for SaveAs
m_FilePath="D:\Build\abc.xlsx"
m_objOpt=System.Reflection.Missing.Value;
m_objBook.SaveAs(m_FilePath, m_objOpt, m_objOpt,
m_objOpt, m_objOpt, m_objOpt, XlSaveAsAccessMode.xlShared,
m_objOpt, m_objOpt, m_objOpt, m_objOpt, m_objOpt);
Now my question is not how to disable compatibility checker,that is
already been answered many times.My question is why compatibility checker
is coming at all.How does excel comes to know that the file is having
traces of excel 2003.D:\Build is empty.