|Connect both router together with a cross-over cable. Turn off DHCP in both routers. Manually configure an different IP address for each router. Manually configure each computer with a different IP address and set each computers Gateway address to the router you want it to connect to.|
Giver each router an IP address:
Set one set computer with an IP address between 192.168.1.2 to 127 and a gateway address of 192.168.1.1
Set the other group with an IP address between 192,168.1.129 to 254 and a gateway address of 192.168.1.128.