why can’t I ping the other computers?

Using 10/100 fast ethernet NIC’s and a 10/100 switch with 3 computers in my home network.Have uninstalled and reinstalled all protocols:IPX/SPX,NETBEUI,TCP/IP.Assigned address’s to TCP/IP(192.168.0.xx Subnet mask 255.255.255.0).can internal loop ping using both 127.0.0.1 and the assigned addresses.can share files and printers with all computers.CAN’T PING THE OTER COMPUTERS.I want to be able to share a dial-up internet connection and to do this TCP/IP must be able to ping the other computers.Ihave removed and installed the NIC’s into other slots and reinstalled the drivers,can still share files and printers but no pinging of the other computers.Have I left out some important detail?