Antivirus is the must have tool to be installed in your system specially if you have any important data. Viruses could slow down your PC and can stole your confidential data. There are some free antiviruses are available that could provide that may be enough for your system security.
Avast Free Antivirus
Avast free version is one of most featured free antivirus. It has option to protect you from real time threats. Scan and remove anti viruses that are recently launched. It take less system memory and user friendly interface that will help you easily to secure your system.
Windows Security: Microsoft Defender Antivirus
Windows security could be another option. It come with your windows and it take less system memory than the any other option. Windows has improved their security service and if you update windows defender on timely basis then you wont need more security options.
Avira is the another free antivirus option. System memory usage is one of important problem and little system usage might slow down your PC. Avira uses less system memory and is update frequently. You can use Avira free antivirus if your system is slow and you need external anti virus option.
Kaspersky Free Antrivirus
Kaspersky is another top rated free antivirus. Their features are recently improved and they also has improved their viruses database.
Free Antivirus Hacks
Most of the antiviruses company provide their free antivirus services that are enough if you are home user. If your system is getting slow in windows 10 then you must use SSD space drive instead of HDD. Also do not install 2 anti viruses in same system as it may hang your PC and you might need to re install your windows 10.