Do I have a virus?

I am recently getting popups from McAfee that my computer is at risk and my firewall is off.  I have windows 8.1 and when I look at my installed programs, it shows that McAfee has just been installed on 3/8/15.  I have had my computer for a year and installed programs shows that most of the programs were installed on 3/7/14.  I have not intentionally installed McAfee. Does it come loaded on Windows 8.1? Since it was just recently installed, do I have a virus?  I thought Windows Defender was my antivirus software and firewall? Help please?