One question that comes to mind is how old is your computer? If it is older than five years old or it has Win98 or older on it then it might be time for a new one.

If it is a newer machine then Microsoft has a utility called "Windows Installer Clean Up." It is available as a free download at http://support.microsoft.com/kb/290301 which might work for you. If you do use it, make sure you only select the McAfee program you want to remove as it is pretty non-discriminate as to what it blows away.

The two last resorts would be to either blow out your hard drive and do a fresh install of your operating systrem OR manually comb through your registry key by key removing anything related to McAfee which I do not recommend for the inexperienced or the faint of heart. Before doing either of the last resort options, make sure you back up anything you don't want to lose.

Best of luck to you!
Bill