the new version is 12.1 this can be installed on win7
http://www.symantec.com/business/support/index?page=content&id=TECH163806
Operating system
• Windows 7 (32-bit, 64-bit, RTM and SP1)
• Windows XP Home or Professional (32-bit, SP3 or later; 64-bit, all SPs)
• Windows Server 2003 (32-bit, 64-bit, R2, SP1 or later)
• Windows Server 2008 (32-bit, 64-bit, R2, RTM, SP1, and SP2)
• Windows Small Business Server 2008 (64-bit)
• Windows Small Business Server 2011 (64-bit)
• Windows Essential Business Server 2008 (64-bit)