Sometimes, McAfee won’t be completely removed if, before, you do not uninstall Avast, including the use of its “Uninstall Application” if necessary (www.avast.com/eng/faq-install-uninstall-avast.html).

This article provides the steps to remove SecurityCenter from your computer.
http://ts.mcafeehelp.com/faq3.asp?docid=71525

If you need, you can find many free versions of these registry cleaners here:
http://www.snapfiles.com/Freeware/system/fwregtools.html