And since you have downloaded a file you new wasn't the right size. Why you did that I have no idea (Curiosity killed the Cat) then opened it. Since you say it doesn't work. Actually it works quite well if you check your share folder there is probably allot of 851.7kb files in it. That file is a Virus and you probably should check out the link below.
http://www.gnutellaforums.com/showth...threadid=41432
Now you can go to the link below if you are unable to get rid of the Virus and Norbie should be able to help you.
http://www.norbiesworld.co.uk/
I am guessing you are not running any Anti Virus software you might be interested in the link below it is free and works good.
http://www.avast.com/eng/programs.html
When you are done with all of that you may want to check out some of the stickies in this forum there is allot of good advice and tips in them on downloading and p2p safety.