If you do not know the password for uninstall,you can modify the registry key and get the uninstallation done
Go to this key
HKLM\SOFTWARE\Intel\LANDesk\VirusProtect6\CurrentVersion\AdministratorOnly\Security /v LockUnloadServices
Make this value 0, this is the password to stop symantec services.. Simillarly
reg add HKLM\SOFTWARE\Intel\LANDesk\VirusProtect6\CurrentVersion\AdministratorOnly\Security /v UseVPUninstallPassword
Make this value 0, this is the password asked while uninstalling...
Hope this helps,