best antivirus for PC

Since the last time my friend came to my computer with a antivirus for PC best, now the computer used to react faster, and the speed is very fast. Although every day at work, I use the computer, but if computer a nothing wrong, I helpless don’t know why do, my computer have to buy a few years of time is always good, but some time ago special card, I want to hold out to repair my of, just the day meet friends, he give me the computer installed a best antivirus for PC, and then the virus just fine, so this time I every day with best antivirus for PC to a computer virus, so now it a special rod.