Stopped using third-party anti-virus somewhere after the initial upgrade to win8.1 when so-called one of the best AV "bitdefender" ultimately slowed down my pc and gave a pretty nice havoc to the performance. Once upon a time my pc was infected with virus and AVG didn't help until the virus decided to spread into system files. So far, never have any issues without a third party AV. Can't say how good, but windefender is reliable, in terms of up-to-date definitions and RT scans.

(Off-topic: Not condemning any 3rd party AV in my post but only certain ones. Some longest and most reliable 3rd party AV I've used are Avast and 360.)

This post has been edited by lolzcalvin: Aug 1 2015, 11:53 PM

I have 16GB RAM and an i7 quad-core processor. The slowdown wouldn't consume only RAM and CPU, but also the hard drive's (disk) performance when the disk usage would be crammed full by the third-party AV (especially bitdefender, avast had no such case). Not SSD though.

This post has been edited by lolzcalvin: Aug 13 2015, 04:32 PM

Virus definition update is important and you should update it. And of course, never ignore any updates in case of tempting to evade any windows updates as well.
Refer to this link: http://www.zdnet.com/article/you-are-doing...ftag=YHR05c7fba