What's wrong with the built-in Windows Defender (which is basically MSE)?
Paid anti-virus software tends to cause more problems than they help, as well as taking up gobs of resources. It's not really necessary to go overblown on security suite apps anyways.
I don't know about other people but Norton Internet Security 2013 is working fine on my system and hardly takes up any resources
The best paid antivirus I've found is Windows Defender, which is currently $15 or $40 depending on which version you buy and is preloaded on all new Windows 8 computers.
I thought that the AV was free.
but it is not an internet security. i think soI've been happily using Microsoft Security Essentials, which happens to be named Windows Defender now on Windows 8 for a few years and it's been solid. 0 problems.