Its probably MSBlaster.
Use this my little script to terminate countdown timer (just run batch that is inside ZIP archive to terminate counter):
http://users.volja.net/razor256/downloads/AntiRPC_Batch.zip

than go to google and type in: blaster removal tool and select some result. I think you can also remove it with avast! Virus Cleaner.
Than search www.microsoft.com for Blaster vulnerability patch.