For Anti-Virus...
I have AVG (free version) and it seems to work fine, regular automatic up-dates.
I also have the registered version of Norton System Works.
Norton, and AVG, don't seem to detect Trojan Horses, the biggest problem for me, but I like "Norton System Works" utilities for automatically sorting out my directory, short-cut, hard drive, etc, problems...

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To detect "Trojan Horses" I have to search the 'Net to install dedicated programs to sort out this particular annoying problem...!!!
"Adaware", and "Anti-virus" removal programs don't seem to detect these dangerous Trojan virus's...

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Cheers all...!
Paul...no virus's....just the occasional Trojan*....

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* Peer to Peer music, etc, download programs...no names, no pack-drill...

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LOL...!
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.