I have used Panda in the past and it worked for me. Being spoiled by open source
and having paid lots for poor proprietary software I am a bit leery of paying
for Windows antivirus software, no matter how good. I choose the freebie one.

Also having to pay extra to protect me from exploits built into the OS rubs me
the wrong way. It seems Iike a tax for the privilege of using Windows. As you
say Mac and Linux users don't have to pay extra to be secure. If Windows users
were not so good natured about it, this would be a problem for M$. Me being me,
I am not so good natured nor charitable. A character flaw to be sure.