best antivirus for PC

My colleagues recently bought a new computer, the configuration is complete, start the software installed, he asked me what is the best antivirus for PC. At that time I did not understand what is the best antivirus for PC, we had to try several, at first thought is the same, there is no any difference, configuration is more appropriate, won’t have what problem, but a friend’s computer is infected with a virus, I realized the best antivirus for the importance of the PC, not to, if the computer has a problem that is the loss of their own, so a good computer to best antivirus for PC. You deserve something good, to deserve their own.