Premium third-party anti-virus software products are both heavy on the system (i.e. slow down the system) and costly. Furthermore, they are known to interfere with genuine applications. Thus most home users prefer not to install third-party antivirus on their systems.

One good alternative to these products is Microsoft's own free anti-virus Windows Defender. However, it is not sufficient. Read more about the same here:

Another option could be installing these free antivirus software products:

Again, they are not sufficient, but good enough.

If you are not using a paid antivirus, it is strongly advised not to install any suspicious freeware or otherwise any unverified software on the system. They push malware on the system.
Furthermore, create a restore point on your system so you could restore your system in case anything goes wrong.