I don't have Mcafee on my computer, but use Norton instead. When I uninstalled it several times while experimenting, I used an app named Revo Uninstaller. It removed Norton 100%, so I imagine it may do the same with Mcafee. If you've already uninstalled part of Mcafee, I'm not sure Revo will work then.
As an alterative, I also like CCleaner's registry tool to clean up remnants of programs that don't completely uninstall themselves. I have yet to experience any registry problems when using CCleaner, but make a registry backup just to be safe. Perhaps create a restore point, also.