This is what someone else told me on yahoo answers–

-”McAfee is not compatible with ANYTHING. Like most anti-virus software, it conflicts with stuff that is supposed to be there on your comp, and even worse with other downloaded anti-virus programs. The best bet is to download AVG Anti-Virus or Avast (I think) and combine it with Lavasoft Ad-Aware or Spybot. One or the other, not both. Those are the least intrusive anti-virus programs. I don’t care much for the new AVG but it’s not nearly as bad as Norton or McAfee.”