replacing mcafee with norton internet security

You should be able to use the Windows Add/Remove Software or if McAfee has an uninstall program use that.  Either one should remove it.  After removing McAfee, restart windows before installing Norton.

Which McAfee product are you using?  Most of the products can be uninstalled using the Program menu path to locate the uninstall for the particular items.

If this fails, or if you also want to clean out the registry entries for McAfee that are left behind after the uninstall, then go to the McAfee site, select 'Support', and select the option to 'Visit customer service FAQ'.  In the search box, enter 'uninstall', and search for the product you're using.