How old is the computer? Did you have any issue with pop-ups or alert in the computer?
Can we have the Version of McAfee software installed in the computer (Open Security center->Click on the about button on the bottom Right hand panel of Security center ->Check the Build number for the)?
What is version of Internet Explorer (IE) you use?
Try to perform the windows update including Optional update (open the Internet Explore Click Tools->windows update)
Perform the MVT in the computer and post the session ID through the link below http://mvt.mcafee.com/mvt/default.asp