best antivirus for PC

If earlier the best antivirus for PC, then installed on the computer, and that I would not be so hard, and this is too much of my own ignorant. Yesterday, my computer do not know how, suddenly opened up, and I have a lot of important information there, so I can only Na Quxiu, to the repair shop inside, the man to help me clean up the computer after a moment, he gave me install this best antivirus for PC, say my computer because it did not install antivirus software, so will poisoning, and later with the best antivirus for PC, so the problem would not be there, After listening to the words of the maintenance staff, and I was assured the