"I have a desktop with windows 7 and ubuntu 12.04 and a laptop with same ubuntu. My desktop is connected to wired network through ethernet cable through a switch. Is it possible to connect and share The internet of my desktop with my laptop? can I use the switch any way, because 5 ports of the switch is still free."
What does the "wired network" that the switch is connected to consist of? There has to be a router in the circuit in order to "route" the internet traffic to the appropriate IP address in the network.
The alternative is to run Internet Connection Sharing in your Windows 7 PC but this does require two network adapters in the PC - one to connect to the internet with the connection "shared" and a second to connect to the Laptop.