Maybe I should post this on "Solved Issues" but I doubt that is what that forum was intended for.
After doing everything possible and still waiting several minutes for the computer to boot, I uninstalled McAfee Virus Scan for the last time and downloaded Avast! 4.8 Home Edition (free). My computer now boots and fully downloads my applications in 30 seconds as opposed to over 3 minutes with McAfee and shutting down also take about 15 seconds as opposed to over 2 minutes with McAfee. Upon my first full scan with Avast!, it found a trojan, which McAfee had missed. My 7 year old computer runs like it is brand new. Every application I use tends to respond more quickly.
I am sorry I waited so long to do this but I know, going through my event logs in Windows, that this problem began after an update from McAfee. I have been using Avast! for over a week and I haven't received one error in the event log when booting!