From KB: 
Title: 'Removing Symantec AntiVirus/Filtering 3.0 for Domino on OS/400 from an AS/400 computer'
Document ID: 2003061209452754
> Web URL: http://service1.symantec.com/support/ent-gate.nsf/docid/2003061209452754

To remove Symantec AntiVirus/Filtering for Domino
1 End all Domino servers.
2 Log in as QSECOFR .
3 Type the following command on the Terminal Emulator:

   DLTLICPGM 7NAVD00
   Note: Be careful. There is no confirmation dialog box.

This command removes Symantec AntiVirus/Filtering for Domino protection from all of your Domino server partitions and uninstalls all product components from your system. Your settings databases are not deleted in an uninstall. This is by design and for the following reasons:
Allows easy migration to future versions.
Permits uninstall and reinstall without losing settings. When you reinstall, a prompt displays that provides the options to keep existing settings databases or replace with fresh copies.

If that fails
here is a link to the manual removal information.

Title: 'Removing Symantec AntiVirus/Filtering 3.0 for Domino on OS/400 manually, when the normal uninstall does not work'
Document ID: 2005021810171954
> Web URL: http://service1.symantec.com/support/ent-gate.nsf/docid/2005021810171954