NAV2009 update/Zone Alarm problem

I've just tried updating my Windows XP Home Ed. laptop from NAV 2008 to NAV2009 and the installation stopped because of a conflict with Zone Alarm, which I was instructed to remove. I don't want to do this because I use an old version (5.5.062.004) of Zone Alarm and have read that later versions cause problems. Is there a way round this? I tried shutting down ZA but to no avail.