search user

I wonder if there is any program that works like audiogalaxy. I mean if there is a program where you can search for a specific user and than get hold of any file that this specific user has on its computer. Of course that folder which is open for any other gnutella user. I have a friend that has over 5.000 files and I would like to reach these files. We both have Kazza and Grokster, but even if I search for a file that only my friend has (it has a very strange name) I get no hits. This mean that I have no contact with my friends register. If you would like to se all files from any user on Kazaa or Grokster you must first get a hit. Why?