Then running the scan it is normal for Antimalware Service Executable to be using almost all the disk access.
When that scan completes, if that indicates no malware is found on your system, go to the support page for your Motherboard on the manufacturers website, then from there, download and install the version of Chipset drivers they recommend and while there, if you do not have your drive encrypted with Bitlocker, check for any BIOS update that may need to be installed