If I have AVG Anti-Virus Free Ed. and IObit Malware Fighter on my computer, do I need to keep these once I instal herdProtect?

herdProtect works in conjunction with all your existing anti-malware programs. I would keep AVG at the very least with herdProtect.

Right, you need a zero day defense mechanism. The way herd protect works, is that it scans files that have already made it onto your computer. So with that said, you need software on the frontline to bounce any malicious activity/malware.

As I just suggested in another thread, I suggest using Comodo Internet Security Premium. IMO, and with evidence supporting this claim: It is currently the best software for preventing threats from reaching your computer.It contains, an anti-virus, firewall, system defense against suspect happenings on your PC, sandboxing and the ability to customize them in every way. So with herdProtect and CIS together, it makes a powerful combination.