Your PCPitstop results were very good. Go ahead and defragment your drive and adjust the browser cache if you have not done so.
We know that enabling your McAfee MSKSrvr.exe is not going to help. Have you emailed McAfee tech support by any chance to ask about the spamkiller hogging the CPU? I would be curious as to what response you would receive. Or I believe there may be an online chat option with McAfee. Sometimes online chat is a pain--slower than talking via the phone but it is free and you do not have to wait for email response which may be a few days. You can hope maybe they have a fix.
You are not alone from what I can find.
http://forums.mcafeehelp.com/viewtopic.php?t=52851
http://www.file.net/process/msksrvr.exe.html