Thanks for posting your config.
I too have used AVG Free on my XP system, and it slowed things down for me too. Windows 8/8.1 is quite a secure system. I use only Windows Defender, Firewall, & User Account Control, which was one of the 1st lessons I'd learned after I'd posted
my config.
That, and first being told about Sandboxie.
http://www.sandboxie.com/ Sandboxie uses what is referred to as a "Sandbox", & my Firefox browser is currently contained in it while I type these words.
Think of a sandbox as an invisible skin that protects your system the way our atmosphere protects the planet. Our environment provides this barrier to threats that come from the outside, & burns them up before they can reach us. Cookies & any changes made to the browser are erased along with the deletion of it's contents. When an update is needed, it must take place outside the Sandbox. This is a cool
way to test how an extension works. If you don't like it, it's not necessary to remove something after deleting the contents of a sandbox. There will be no trace of the extension, or any other add-ons tested while sandboxed.
PS Here's where you can find HitMan Pro
http://www.surfright.nl/en/hitmanpro/ & Malwarebytes Anti-Malware
http://www.malwarebytes.org/free/