File shared to my HP, now I see neighbors computers under Shared in OS X

[98707]

I was messing around to wireless transfer files to my HP laptop from my Mac Pro. I ended up getting it to work and then I turned off file sharing. The next day I notice that under shared in my finder and in itunes I can see between 2-8 PCs and Macs in my building which are not supposed to be on my wireless network.

I have all types of sharing disabled.
I have an Airport Extreme 802.11n password protected.
(I changed this password too)

I want to have itunes share music privately on my wireless network. However, now with all sharing disabled I see all these computers in my itunes when I look for local shared itunes.

Can they see my computer? Why do I see them? How do I hide these computers?

I found some interesting things here but they don't provide any real solutions that have worked. Has anyone encountered this before?

http://www.macwindows.com/leopard.html



Thanks-