There is a completely free version of Zone Alarm - I've got it on one of my laptops & so does DS - presumably you've got a trial of the paid-for version.
You do have to spend a bit of time teaching it which programs to accept, but it just means clicking OK when it asks, and the last MS update managed to knock a lot of ZA users, including DS off the internet for a bit, but it's been fixed now.
When you install the Free Version of Zone Alarm it asks you if you want to install a 3 month trial of the full software. Say No - Continue with Free Edition. Then you won't be pestered to part with money. Add in AVG Free for Antivirus and you are sorted.