Computer listed in Finder. How do I remove?

Finder > Preferences > Sidebar and untick it from there I Think

If you mean in the Sidebar on the left side of a Finder window, right or control click then click Remove from Sidebar.

If you hover the cursor over the name Shared to the right another label will come up that says Hide. Click on that and it will remove the Shared section in Finders side bar.

You can also try holding down the Command key while dragging that item out of the Sidebar.

If the share is on your network, you can't break the link. The person needs to stop sharing so everyone on the network doesn't see it. If that's not possible, then each user would have to remove the share from their Finder Sidebar.

There really isn't a Link between your computer and the ones listed in that area.

It is just showing you other computers that are available on the same network, LAN. If you clicked on any of them it would ask you for a user name and passord to connect to it. The same thing happens if someone else on the same LAN, network, tried to connect to your computer. If they did not know the correct username and password they could NOT connect to your computer.

As I stated above there is no LINK between your two computers.

Exactly where is it on the list in the left hand side of Finder?

Is it in the heading Shared, Favorites or Devices? Or some other heading on the left hand side.

If it is finding and displaying your friends, mates, computer name then it is on your network (LAN, Local Area Network).

Is your Mate in the same dorm room as you? In the same building as you? Going to the same school as you?

All computer today are set to look for other computer connected to the same LAN (Network).

When you put the cursor over the Shared label you should see a popup to the right of it that says Hide. Click that.

First it's not a dilemma. Having that there mean nothing other then both of you are on the same LAN and the computers list in that area have Sharing enabled. Even if you don't have sharing enabled other computer that do and are on th same LAN will show up in that area. Noraml and nothing wrong with it. As I said above Hide the Shared section.

I fail to understand why you are so concerned about this. If this is your friend. He can not connect to your computer if he does not know your password.

Disconnect yourself from the internet, unplug the Ethernet cable and or turn off WiFi.

Go into Keychain Access and delete the entry for the connection to your Mates computer.

Restart your computer. Re-connect the Ethernet cable and turn WiFi back on.

Is it still listed?