This is interesting - Downadup and Conficker worm - At this time 15 million computers infected.

See here for brief description:

http://www.ehow.com/how_4721828_avoi...cker-worm.html

And here for one removal:

http://www.bleepingcomputer.com/malw...adup-conficker

This is alleged to infect large company networks more than others. Did not find but two references to it on Virtual Doctor.