I've had a nasty infection on my PC--the Trojan.vundo.H trojan horse. I had Mcafee but it didn't seem to help. Mcafee was disabled every time I booted up my computer.
I looked for a solution on several forums and tried to follow their instructions--nothing worked. The programs I used would find and (temporarily) remove virus, but it would be right back as soon as I rebooted the computer.
After a few hours of this I decided I'd be better off just reformatting my PC. I've rebooted and installed AVG (and superantispyware as an additional layer of protection). Both of these are free--I don't see the use in paying for a Mcafee subscription again this year.
This issue has made me appreciate my MacBook all the more.