To completely remove a mcafee program, you uninstall it using the regular Windows way and THEN, you run this program: MCPR.exe, I have a link but unfortunately I don't know how to post it here, it's removed from my post if I try. Do a Google search on "mcafee removal tool". Make sure you download it from an official McAfee site.
FWIW, I visit many Windows newsgroup and forums and it's a known fact that if you run more than one antivirus program you could run into troubles. For example if you don't like MSE and prefer Avast, install Avast and uninstall MSE.
Win8 comes with Windows defender, if you install a third party AV program, defender should be deactivated. The installation process of the third party AV might be able to do that.