Sylink is stored here:
Win7: C:\ProgramData\Symantec\Symantec Endpoint Protection\CurrentVersion\Data\Config
XP: C:\Documents and Settings\All Users\Application Data\Symantec\Symantec Endpoint Protection\CurrentVersion\Data\Config
As others have said, you should really be using sylinkdrop or the client GUI to load the new sylink.xml file since everything in the client is now tamper protected (even when our services are stopped).