There have been no previous problems or viruses detected on my Win 10 laptop but today the scan is stuck at 0% and does not show any files being scanned althought the wheel is turning. I have tried re-booting but no improvement. Any suggestions?
You could uninstall McAfee. It's not particularly robust and consumes an inordinate of resources, even when it works as intended. There are other free Anti Virus programs available. Have a look at Avast and ZoneAlarm.
