I have my Pc running on the operating system XP OS. I already have the Office 2003 running on it and am planning to get the Office 2007 installed too. Will this cause a problem? I really think it should not consider the compatibility option in both systems. The only question I have is if excel files and macros would work similarly in both options? Or will it be stored in two separate workbooks? Or will I be able to use the same workbook in both the systems? Do you have any suggestions that I must keep in mind?