I have a network at home: three wired PCs (various operating systems) and one laptop with Windows 7 Home Premium.
I have the following issue with the laptop: when I connect it to my network using a cable I can see the rest of my network computers and they can see the laptop.
When I connect it through wireless the other computers are lost .... and my laptop also becomes invisible to the other PCs (but I can always access the Internet). I tried disabling the firewall on the laptop but no luck.
There may be a setting in the router configuration for this. Maybe something that allows wireless and wired connections to see each other. Go to the router setup in whatever browser you're using and look around. It's usually http://192.168.1.1 or http://192.168.0.1.
It would help if you let us know which router you're using.