Sharing Folder across the Routers.?

Routers will block incoming requests. Only if you know what ports are used by the file sharing, you could open them in the router. However, most home routers do not just "open" ports, they require port forwarding to one PC. That will not work. Separate routers make separate networks. To access any common "share", it would have to be placed on the very first sibnet (on router plugged into modem). All other routers can then get to that share, since all traffic has to go through that first router. Putting a share on any secondary router will block access to anyone on the first router, and very difficult to get around it.

Thus, any "shares" must be on the first subnet only. Only other way around it is to just use one router and multiple switches - forget about multiple routers if you do not need them.

EDIT: To use other routers as wifi access points, wire all routers as "switches and AP" only. Use just the LAN ports. Configure each router with a static LAN IP on the first subnet, and use just LAN to LAN ports. I've described the process before (though the wifi SSID may be messed up, it does put all routers on same subnet):

http://answers.yahoo.com/question/index?qid=201011...

Sub routers are installed only to give Wi-Fi access withing home. Our houses are on some distance hence we can't use same Wi-Fi.

We also can't use any computer as server. and also can't buy new devices.

Whatever we can do is just change some configuration in Routers setting so that we can be connected with each other.

For the number of computers you have mentioned, your network architecture sounds excessively complicated.

If you are trying to share files using Windows networking, then all your computers really need to be on the same sub-net.

If you have different sub-nets, you should be able to create a map from a computer on a subsidiary sub-net to a drive on a computer on the parent network. You will have to use the IP address of the computer you are mapping on to and not the computer's name. You may need to have the target computer on a static address to ensure that the mapping works each time you start up the network.

To go from a parent sub-net through a router to a subsidiary sub-net, then you will need to configure port forwarding. This may limit the connection to computers on the subsidiary sub-net to a single target computer.

Unless you have a very large number of devices - perhaps more than 100 to 200 machines - and you do not need to isolate machines by putting them on different sub-nets, then you should probably reconfigure your network into a single sub-net.