What is the best Antivirus?

By far Kaspersky is the best. Try the 30 day trial period first. The Russians know their stuff when it comes to making viruses and the protection against them.

http://usa.kaspersky.com/downloads/free-home-trial...

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Microsoft Security Essentials

Krishnan is on the right track. It is difficult to pick a BEST. The Department of Defense used McAfee. I've worked with corps that use Symantec/Norton.

I use AVG, because it is free (free for life) and has worked really well. With ~300 viruses out a month, some will slip through, especially zero day attacks. Avast may miss one that AVG picks up and vice versa.

To download AVG antivirus (free.avg.com), make sure you pick the free one; it is close to the paid version. Make sure you update the antivirus after you have it installed.Then do an initial scan.

Restart your computer and hit the f8 key at the top of your keyboard (approx. once every second) while the computer is starting up. You will see a text only menu of options. Select "Safe Mode".

It looks like garbage all over the screen. Be patient. It will eventually get you into Safe Mode. Once you see the usual familiar graphic Windows look, find the AVG installation and run it to scan for viruses. Safe Mode disables all but necessary services. This includes viruses, so it is easier to get rid of "smart viruses".

After that, the antivirus will prevent infections.

Well, none of them are the best. But I would personally recommend Avast. It provides downloadable setup for both installation and virus updates. If you don't have internet connection you can download virus updates from other internet enabled computer. The only disadvantage is even for free edition you would need to register for the product key. But a simple registration is not a big deal for 1 year free basic security.

http://www.avast.com/free-antivirus-download

Bit defender Antivirus Plus

if ur windows is genuine go for Microsoft Security Essential ^_^

E-set, kaspersky