security question

I was just in the public library doing some work and I noticed something that made me pause.

While using their network, in my finder I could see the hard-drive of someone near by. I didn't poke around but my concern is how "open" do I appear and more importantly what should I have set in my preferences so that no one can see or have access to me.

I am running 10.5.6
I have a home wireless network that my MBP is the only computer on it.

I should also say that i have switched to Mac only recently after years of windows based knowledge. So I learn something new every day it seems.

thanks in advance

Your mac is pretty secure

basically, out of the box os x only opens a port to connect to a network

ubless you have elected to share your mac, with other macs (sharing) or to share with other windows users (windows sharing) you are safe

Even if you have enabled those ports, other users will still need your user name and password to see anything on your mac

so rest assured

thanks for the knowledge