Parent / child subnet file sharing

I was having trouble getting my WDTV Live to read file shares of my XP box and I realized it was because I made a stupid oversight.

my pc’s were connected by wire to my modem (which has a built in router (the parent network)) but I also have a wireless router thats connected to my modem that gives wireless signal (the child network) to all my wireless devices (such as WDTV Live)

thus the wireless devices are actually on an entirely different subnet than my pc’s

so all i have to do is disconnect all my stuff from the modem and connect it to the router directly and it should solve the problem.  However for logistics reasons i would like to leave my setup the way i have it so i would like to know is there any way to work around this setup and still have this work.  Essentially i would have to find some way to bridge the two networks so that WDTV Live will search the modem (parent) Network as well.

is this at all possible?

Unless you unify your network under a subnet, I don’t think this will be possible.