Sounds like you're better of, not using NSS. I do think Avast! is a good product, but if you have money or use the
promotional 6-month Norton Antivirus, you're good to go.
I found that Norton 360 (2011/2) can screw up your PC, with it's registry cleaner. That said, the new version could be different. However, CCleaner and other tools are safer to use, as Norton generally turns out to be automatic solution (user has little control).
Let's not forget, Windows 8.1 has a very good firewall, so Avast! Free + Windows Firewall can provide good security.
Example: Even the new Avira Free 2014 integrated Windows Firewall into it's GUI.
aztony said:
AFAIK, NSS is an all-in-one solution that includes firewall, whereas Avast free is AV only.
Thanks.