Hi my friend, I try help you.
Do you have config your network on all computer ?
Your internet is connected on Modem, or the router... I prefer, that you connect on Router... same me
Ok second step go to "Network" under "my documents" now check at left many option you have it... take "Create a Network for home or company" Make the connection with the assistant : enter name MSHOME as name for your network... and the name of your computer... is your choice
Try it... and gives us your news !
Good Luck