In November 2008, a worm, dubbed 'Conficker' started spreading through Windows-based PCs and lurking dormant in the background. The virus is set to be activated tomorrow - no one knows how many computers are infected, but estimates are as many as a few million. The worm will allow Conficker creators to steal information from your computer, send out spam emails from it, attack other websites from it, or possible wipe out your files.
Below is a link to resources to help you find and get rid of this virus if it's on your machine:
7 Resources to Help You Prepare for Conficker's D-Day