I'm using a low-end desktop, i've tried using ZA as my firewall and Norton AV both of this software rely heavily on my system resource i've been searching for other softwares to replace them. AO users out there can you suggest me a firewall and antivirus that is reliable up to the job and less resource hogging like ZA and NAV?

I'm also looking for a browser that can block pop-ups and ads. IE hangs and crash on me whenever i visit a site where there are alot of flash banners and my IE just went dead.