I am a bit of a newbie myself but from reading the info pages on web sites like limewire.com i believe the system works as follows. all your search requests goto the other computers you are linked to in the host section of limewire they send on your search requests to other hosts/users and so on. when one of them has the file you want they send that info back and if you download you download the file staright from the computer that has the file you want. you never need to search the whole of the gnutella net as the system is designed to have duplicate copies of files all over the net so that if parts of the gnutella net fall down you can still get the file you want. the point of the gnutella net is that the system is completely decentralised and therefore is unable to be attacked or stopped