Hi Sansan,
Sorry for not responding sooner.
Please go to \System\Library\CoreServices\SystemVersion.plist file. Open the file in TextEditor. What does it have for ProductVersion?
In the same location, can you check to see if there is a ServerVersion.plist file? If so, is your system a server?
Did you upgrade your machine from 10.6.8 directly to 10.9, or from some other version?
--
Maria