Can't see all computers on XP home network

Hello,
I have three computers running XP home on 2 and Xp Pro on the other. I also have a laptop running Vista home. All are connected to a 2wire 1000SW gateway/router through a net gear network switch. All computers are running norton protection software offered by ATT. The problem is that I can not get the file/printer sharing to work. I have all the file sharing and print sharing enabled. The 2 wire router sees all the systems. but the computers don't see each other. What do I have to enable or disable to get it to work. thank you for any help you can give