Same as Sandra @ 12:41.
The problem with Macafee is they often 'piggy back' on other downloads and unless you are careful it gets loaded. Some PC's used to have it preinstalled too, although I dont know if thats still the case.
As for the OP, you dont say whether McAfee is the virus software being used or its something thats 'just appeared'.
If it is the software installed dont ignore it. Load some other anti virus such as Avast (free) disconnect from your network and see if that finds anything. If it does then get it to remove or quarantine the problem.
If McAffe is not your virus software what is?