It's been my experience that McAfee doesn't like to be uninstalled. They leave little bits of McAfee all over your system to antagonize you so that you reinstall it. I had to search the registry for "McAfee," to find all the instances of it that remained after I tried to uninstall it. And I had to be careful that I wasn't deleting some other program that simply had the word "McAfee" in it.

I suspect there are programs that will clean it out of your registry safely. Find one and download it. But check that it isn't a virus itself.