Because you have connected a wireless ROUTER to one of the switches, the computers connected to it will be in a different Subnet from the computers connected by ethernet to the main router. By default, Belkin routers operate in the 192.168.2.0 subnet, i.e. the router will have the address 192.168.2.1 and allocate addresses by DHCP between 192.168.2.2 and 192.168.2.254
Your main router possibly operates in the 192.168.0.0 or 192.168.1.0 subnet and it is the purpose of the Subnet Mask (255.255.255.0) to prevent these different subnets from communicating, i.e. it "masks" them.
If you had connected a "Wireless Access Point" instead of a router (presumably a Cable/DSL router?), computers connected to it would still be allocated an IP address by the main router's DHCP server and therefore remain in the same subnet.
You might get it all to work if you give the main router the IP address 10.0.0.1 with Subnet Mask 255.0.0.0 and the second (wireless) router the address 10.0.1.1 with the same Subnet Mask. This different Subnet Mask address should allow the two subnets to communicate.
If that isn't successful, or you don't want to meddle with the IP addressing, disable the wireless router's DHCP server and connect its incoming ethernet cable to one of its LAN ports instead of its WAN port. It should then function as a basic network switch and wireless access point.