Microsoft Security Essintials. I'm a Certified Ethical Hacker, and i can tell you that no Anti-Virus is 100%. Also, you should never pay for anti-virus, as all AV programs get their definations from the same source. Much like gas, it all come from the same pipe line, its just distributed from there.

Agreed with the above, used to use AVG as it's free and thought it was good, then when copying files to a new machine which only had Microsoft security Essentials, realised how poor it actually was at doing its job....

So yeah, a vote for MSE from me

Nod32 + Comodo Firewall + Malwarebytes that's my combo. Whatever your downloading get it from a reliable source.

Well I've tried AVG and it sucked badly then I spent almost a $100 bux on that Norton Garbage and with in 2 day's all three machines I had installed it on had to have the Hard Drives reformatted and all even the one that I had just installed Windows 7 Ultimate x64 and done nothing else with. Norton's Customer Service stated it was a problem with the machines and I didn't know what I was talking about but I ran another Anti-Virus (Kaspersky) off it recovery CD and it found a whole Boat load of Viruses! so that was a Major Waste of money just because I thought Norton had finally gotten better from a review I had read in CPU Magazine. Then I started doing research and discovered the Kaspersky was the best out there in all of the test so I gave it a try from the copy on my Motherboard CD and never had a problem since! it's so good I even went out and purchased the 2012 version and installed it. So my recommendation would be Kaspersky all of the Way!