No single antivirus detects ALL viruses. I have Avast and I use Panda's online ActiveScan once in a while for a second opinion. So, it is good to have Mcafee, at least you have something, but also use some other online antivirus regularly to double check. A list of online scanners is available here:
http://forums.techguy.org/general-se...elp-tools.html