Hi,
Symantec Antivirus 8.0 reached its End of Support Life as of November 30, 2005 and Symantec Antivirus 8.1 reached its End of Support Life as of January 31, 2007, as defined in the Symantec Enterprise Technical Support Policy. Therefore virus definition updates are no longer supported for this product.
Symantec Antivirus 9.x has reached its End of Standard Support as of March 31, 2009. Virus definition updates for version 9.x will be discontinued on April 1, 2009.
http://www.symantec.com/business/security_response...
You can't directly upgrade to SEP 12.1
Supported upgrade paths for the legacy vesions are as per the below:
SAV 9x & 10.x / SCS 2.x & 3.x / SSEP (Sygate) 5.1 --> SEP EE 12.1
If planning to install SEP 12.1 then it will be a fresh install for you.
I would also strongly recommend to upgrade to the latest version of SEP.