I see a real false sense of security in several posts. A little research will show you some actual numbers. here's one of many sources:
MS Security Essentials - Ouch (0 / 6 rating)
http
/www.av-test.org/en/antivirus/home-windows/windows-7/august-2014/microsoft-security-essentials-4.5-143171/
Avast - Better (3 / 6 rating)
http
/www.av-test.org/en/antivirus/home-windows/windows-7/august-2014/avast-free-antivirus-2014-143113/
Comparative List
http
/www.av-test.org/en/antivirus/home-windows/windows-7/august-2014/
Useless ?, tell that to the peeps who have lost valuable information or paid $100's of dollars to have their machines restored. I have disinfected people's PCs and reported infections to their AV software providers that they denied existed .... for 3-4 days, then they admitted that they missed a new one.
It's not a matter of just being competent and careful, what matters is is everyone you know or come in contact with careful and competent. 9/10 Windows PCs I am asked to look at because of resource or slowness issues are infected. Just last week (11/11) I downloaded a software update for a utility I have been using for ten years. It had a infection which my software detected .... luckily, what I was using was 1 of only 3 programs that were then capable of picking it up.
https
/www.virustotal.com/en/file/d8d339b26e68ac6e6ac6e5fe1d53a0274de3bfe1ea35c4b2d4aca5885386b6fa/analysis/
Now there are 9 programs capable of picking it up. With 0 day attacks, you are only as safe as your vendor's ability to update their definition files and / or the capability of their Hueristic abilities.
As far as the lifetime subscription to Malware Bytes .... still available for $20 (1 PC) single purchase