But honestly if you suspect a problem with the computer, should also have Malwarebytes on it to scan for Malware and remove it. ALL ANTIVIRUS need to go 'online' as Day-ZERO is the most common viral codes that are out there. You can put your PC online and download one of the Free Antiviruses like Panda, Avira, AVG, Avast, and install that then run the scan.
Windows Defender doesn't perform to the level that is acceptable to even block or get rid of 50% of the viruses out there, and certainly not the Malware, which is the most common cause.
