Avast Antivirus for Windows is security software that prevents viruses, spyware, and malicious threats from infecting your PC. Here the topic includes instructions to download and install Avast Free Antivirus software. Avast One Free is an all-in-one security tool that blocks viruses, spyware, and malicious threats. And, it protects your computer and device data from hackers while you browse online, and improves the performance of your computer system. It is available as both a free and paid product. Here topic explains how to install the free version of the app.Now Avast One Free is installed but may some components not fully function until you restart your computer.