Help!!! Am I on a network?

[i know nothing]

Something quite bizarre.

I connect to the internet through a gateway, whatever that is. I was playing around installing a new firewall and I went wandering into network places. There on the screen I see a folder that is clearly someone else's work folder on their machine. I have complete access.

Does this mean I am on some sort of network and that people can get access to my machine?

How can I check to make sure no one can do the same to me?

How can I disconnect from the network this other bloke is on? Presumably if I can see him, he can see me?

Some screen shots:-

 

[Berserker]

Get a software firewall and set it to block incoming connections unless you specifically need them. Even Windows firewall will do (I think). Job done.

 

[csmager]

How can I disconnect from the network this other bloke is on? Presumably if I can see him, he can see me?

Easy. Take the cable out.

If you're connected to the same router, you're on the same network. You're probably not sharing anything, but a firewall would make sure of that if you're that worried.