I have a small home network,2 PC's.Before doing anything,check out the friend's computer that is receiving the internet.See if they are using Window's firewall.If they are, see how it's configured. My client PC,wasn't getting any Internet signal,but my host PC was.I had to disable Windows firewall to get a connection.I then downloaded a free firewall(in my case Comodo),and it worked.
note: each time you run The Network Connection Wizard,Windows Firewall will automatically turn back on.You will have to disable it again.
Hope this helps.I'm a bit green at this too,that's why I joined this forum today.
Good luck,mellow.