SEP 12.1 does not support Wndows 2000 and will not install.
System requirements for Symantec Endpoint Protection 12.1.6 MP1, MP1a, MP2, and MP3
Here is what's supported by 12.1.6:
Operating system (desktop)
- Windows XP Home or Professional (32-bit, SP3; 64-bit, SP2)
- Windows XP Embedded (SP3)
- Windows Vista (32-bit, 64-bit)
- Windows 7 (32-bit, 64-bit, RTM and SP1)
- Windows 7 Embedded Standard
- Windows 8 (32-bit, 64-bit)
- Windows 8 Embedded (32-bit)
- Windows 8.1 (32-bit, 64-bit, including Windows To Go)
- Windows 8.1 update for April 2014 (32-bit, 64-bit)
- Windows 8.1 update for August 2014 (32-bit, 64-bit)
- Windows 8.1 Embedded (32-bit)
- Windows 10 (32-bit, 64-bit)
Operating system (server)
- Windows Server 2003 (32-bit, 64-bit, R2, SP1 or later)
- Windows Small Business Server 2003 (32-bit)
- Windows Server 2008 (32-bit, 64-bit, R2, SP1, and SP2)
- Windows Small Business Server 2008 (64-bit)
- Windows Essential Business Server 2008 (64-bit)
- Windows Small Business Server 2011 (64-bit)
- Windows Server 2012
- Windows Server 2012 R2
- Windows Server 2012 R2 update for April 2014
- Windows Server 2012 R2 update for August 2014