Hello,
Could you please PM me your Case #?
Windows 2003 R2 is fully supported with SEP 12.1 RU2 and SEP 12.1RU3. http://www.symantec.com/docs/TECH195325
Could you help us with the SEP_Inst.log file from the server machine?
Till that time try the following steps:
Check this Article:
Steps to prepare computers to install Symantec Endpoint Protection 12.1 client
http://www.symantec.com/docs/TECH163112
Steps:
1) Open registry and go to
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\
hight light Session Manager on the right hand side delete the value PendingFileRenameOperations
2) Also delete the same value from
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet001\Control\Session Manager\PendingFileRenameOperations
then run the install...without rebooting the PC
http://service1.symantec.com/SUPPORT/ent-security.nsf/ppfdocs/2007121609023348?Open&dtype=corp&src=&seg=&om=1&om_out=prod
Reference: https://www-secure.symantec.com/connect/forums/endpoint-protection-will-not-install-0#comment-7532391
Hope that helps!!