"Cable Modem --> Unmanaged Ethernet Switch --> Computers (#1 & #2)"
The problem with this setting is the Cable Modem assigns different Subnet Masks to the two computers. Having the same Subnet Mask is mandatory to have a Network between the computers. The solution is to disable DHCP and manually set the IP Address, Subnet Mask, Default Gateway, Preferred DNS Server, Alternate DNS Server. To do it first make a note of the above parameters by using the command "ipconfig/all" at "Command Prompt" on both the Computers.
On both the computers goto "Start Menu --> Settings --> Network Connections --> (Right Click) Local Area Connection --> Properties --> (General Tab) Internet Protocol (TCP/IP) --> Properties". Select "Use the following IP address:"
Enter the following:-
On Computer #1
IP address: = IP Address of Computer #1
Subnet mask: = 255.255.255.0
Default gateway: = Default Gateway of Computer #1
Preferred DNS server: = Preferred DNS Server of Computer #1
Alternate DNS server: = Alternate DNS Server of Computer #1
On Computer #2
IP address: = IP Address of Computer #2
Subnet mask: = 255.255.255.0
Default gateway: = Default Gateway of Computer #2
Preferred DNS server: = Preferred DNS Server of Computer #2
Alternate DNS server: = Alternate DNS Server of Computer #2
Click OK, OK.
