The IT guys just told us about a new worm called Downandup, Downadup, Kido!, or Conficker (all the same worm). It seems to be be delivered using infected USB drives. The worm hijacked the autorun program and shows a default selection on a fake download screen that looks just like the Windows download screen. The problem is that it shows installing it’s own virus as the default choice on the screen. So of course most people are going to click on it and then it is too late.
I use USB drives all the time but I only transfer specific files from the jump drive to the PC in use. I never use USB drives to install programs and although it is not foolproof, I think that is a good policy for others to follow. But if you have been infected, a site called F-Secure has a removal tool that should get rid of it.