I'm confused over your thread title and the McAfee problem - it's probably my age.
Can you still go online and surf websites normally? Can you go to http://www.speedtest.net and take the online speed test the post your results back here? Ignore the offer to Scan Now for so-called PC errors and just take the speed test.
Maybe McAfee has a problem at their site - did you see an offer of a choice of mirrors? Mirrors are other sites from which to download which might be faster.