What is the easiest way to go back Norton Anitvirus 2009 after upgrading to version 2010?

I work at home and recently started using a newapplication that requires I go into a Citrix Lockdown Desktop.  I am told to ‘disable’ Norton before going into the Lockdown desktop.  However, when I start the process I get a message that says that I need to ‘turn off’ Norton Antivirus manually. The program is not able to turn off NAV.  My delimma is that even if I turn off Norton antivirus protection, I stil get the message.  I just upgraded to version 2010 and would like to try the lockdown desktop with the previous version.  How do I go back to Norton Antivirus 2009?