It happens to the best of us...
What do you get when you combine a busy evening, an ongoing IM chat and a moment of inattention? You get what you see to left of screen.
Note that I declined the download... don't play with with fire by downloading the virus, even if you know what it is and just want to experiment.
My infected correspondent is a high-calibre computer professional - right up there with the best of them - but as this incident shows, even the best of us make mistakes.
For what its worth, the PC was isolated from the internet within 5 minutes of the infection occurring. No word, yet, on how easy or difficult it was to clean, or if it was given a name by the clean-up tools used, but from what I can see it was this one: