Yeah, you've downloaded a file with a virus. Always scan a file with your AV program before you open it.
See point 4 here
http://www.gnutellaforums.com/showth...threadid=41432

Go off to norbiesworld & register (it's free), he will help you get rid of the virus. There's a link to his site in the above thread. Please read the whole thread, being careful will prevent this happening to you again.