What is the best computer security for personal computer systems?
That is a very broad question. Of course the most secure would be to have no internet connection what-so-ever, but I suspect that’s not what you mean. The best security would probably be using some form of Linux (Ubuntu is fairly easy to operate now), for the simple reason that very few people can be bothered to write a virus for something so obscure. But if you insist on using Windows, use something like Comodo anti-virus, which provides virus scans and real-time execution prevention as well as heruristics and a firewall. Ensure that it is always up to date and set it to ‘Paranoid mode’. That way it will stop every 4 seconds to ask you whether you REALLY want to let Microsoft word access the key buffer, or simmilar inanity – it’s massive overkill. Just keep your anti-virus up to date, on ‘normal mode’ and you should be fine.
