Mcafee is considered one of the best antivirus application. It keeps on working continuously to protect your device from unwanted attack. Therefore, if McAfee slows computer to a crawl then there might be any other unwanted or suspicious application running in the background that needs to be stopped on an immediate basis. Otherwise, it may steal your data. However, if you feel that it is not dangerous then you can simple disable McAfee temporarily to keep your computer actively without trouble.