So you need to Scan your computer by a full version of antivirus programs and don't ever go for the free version of antivirusues as they slows down your computer and asks for updates very frequently. Updating antivirus invites viruses to download in your computer along with the update files. Full vewrsion antivirus program won't ask for updates at all. And maintains your computer's speed and performance.
What in the hell are you talking about?
There's a lot of free antiviruses that are loads better than the crap you pay for (Norton / McAfee). MSE, Avira, AVG... all free and good. All AV's ask for updates when they need to. If you're saying that paid AV's don't update.. then they're not doing they're job. Virus signatures change and new malware is formed... AV's HAVE to update otherwise they're not going to work right.
How does updating an AV invite viruses to download alongside the update? You realize that potentially exists with almost everything that connects to the internet, right? McAfee and Norton hinder performance because they're overbloated, retail crap. The only paid AV that's good is Eset Nod32; that's the only AV I'd be willing to pay for.