Hello,
What version of SEP (11.x / 12.1 ) are you running?
In case of SEP 11.x, Sylink.xml for win 2003/2008:
C:\Program Files\Symantec\Symantec Endpoint Protection
In case of SEP 12.1, Default Location of the Sylink.xml file
(Note: Be sure to configure Windows Explorer to show hidden folders.)
Windows Vista/7/2008/2008 R2: Drive:\ProgramData\Symantec\Symantec Endpoint Protection\CurrentVersion\Data\Config
Windows XP/2003/2003 R2: Drive:\Documents and Settings\All Users\Application Data\Symantec\Symantec Endpoint Protection\CurrentVersion\Data\Config
Secondly, to In case of replacing the sylink.xml file, check this Article:
How to change the sylink.xml file in Symantec Endpoint Protection (SEP) 12.1
Hope that helps!!