Regardless of whether you choose Windows Defender Antivirus, or a third party antivirus solution you need to be sure these products are not scanning critical File and folders because Occasionally Microsoft Security Essentials or Windows Defender cause problems with some Files and folders.
Typical issues include slow performance , deleting some necessary files or erratic operation or it may flag a file or folder that you trust as malicious. To work around these problems you can add this kind of files and folders to the list of exceptions.
Download
Defender Exclusion Tool 1.4.zip - 3.7 MB