Bummer, you've probably caught the Blaster Worm

Update, May 2004: You might also have the Sasser worm; see below

You'll be happy to know it's fairly easy to get rid of:

1) Boot up your computer. 
2) Click the "Start" button 
3) Down at the bottom of the start menu, click "Run..." 
4) Type the word "command" (without the quotes) and click "OK" or press "return"


a blank window with a prompt will appear -- 
this is called a "DOS Box" or "DOS Prompt"

5) Type the following and press Enter: shutdown -a  
-- that will stop your computer from shutting down.
6) Go to this page
7) Follow their directions to download and run the 
Symantic FixBlast removal tool. 

Once you run fixblast.exe, go to the Miscrosoft site
 to download the patch.

Sasser has a similar appearance on an infected computer: the computer will probably slow to a crawl (as the worm tries to reproduce itself, it spawns 128 threads, which consume a huge amount of CPU power) and it will also cause the computer to shutdown with the "computer shutting down in 1 minute" warning.