If McAfee isn't up and running, then the real-time scanner shouldn't be active. Basically, just there and watch that process for a while and see if it keeps pinging the
CPU column.
Ctrl-Alt-Delete, Processes tab, then just watch the McAfee process for a few minutes while you open files and surf the web (leave the task manager open, it will stay on top of every window). I'm imagining it is just going to sit there and do nothing since the program isn't actually open.
If it is still pinging the
CPU constantly, I would just use the McAfee removal tool and get rid of it forever
Trend Micro Internet Security is my preference

$59 for three licenses. Takes very little resources, easy to use, good customer service.