what is "owner-pc-vaio". its in my shared column in Finder. would another computer using my wifi show up in the shared column?

If you have sharing enabled, yes.

Sounds like you need to change your router's network password. Use WPA2 personal if at all possible.

Yes it would show up.

Sounds like their sharing is on and you are seeing someone on a sony vaio computer on the same network.

If you're in a hotel, school, or someplace with public WiFi access, you'll see a list of all other computers on the network.

As opposed to the answers above, with or without sharing on, you will see others on the network and they can see you. As long as you have sharing off, and even then, they'd not have unrestricted acces unless you disabled all password access, they can see you but they can't do anything.

If you're on your own private network, someone is stealing your bandwidth. Since it's a piece of junk Windows computer, you can find out how to send them a nasty virus over a LAN. 🙂

Agreed.

They will appear if your sharing is off but theirs is.