Do I reinstall Avast! Free Antivirus to get vivus protection?

I send my computer for in a repair shop this summer they not so great around my neighborhood is my opinion and I don't think my dad is going to go back there again.The guys where the ones that put vivus protection on my computer and its call avast! Free Antivius it suppose to protect against vivus and spyware.Once in an while I just click quick scan and Full system scan that's all its about to expire today and then I would have to select base protection which I don't know what's that or register the full protection which is 19.99 I won't paid it I also can't open Mozilla Firefox it keep saying that they encounter a problem so I'm using Internet explorer.How can you guys help me out? Please no scan I don't know what type of Antivirus I have but I stop by a page and this is a link of how it looks like the only thing is that it never did said additional protection on the screen everything else is good.