Check it is gone when you run 'Uninstall Programs' in Control Panel. If still there uninstall again. If still causing problems -
Run 'Services.msc' add check for McAfee entries. If you find any, Rt click them and select 'Properties'. Change Startup Type to 'Disabled' and Recovery to 'Take no action'
Remember to install anti virus, like 'M'soft Security Essentials'