Hi,
I think I get more confused as I read your responses. If I get it right, you are using 2 routers, one a combo modem / router which you are using to handle DHCP and the second as a "gateway" in some mode bridge, repeater, ap or what? Then you have a "network" which consists of a W7 machine and the 320 does not show up in the W7 Network and therefore, you can't map the 320 as a drive. And you have "NAs connected to both first and second" router. How is that possible?
Using 2 routers together sucessfully can be difficult and with some combinations impossible. I have to suspect that there is something with how you are using the 2nd router, not sure why you would do that unless your 1st combo router has only one ethernet port, and in that case, I would suggest you consider an inexpensive switch for additional ports. I would also skip using static ips at first and let DHCP handle the initial assignment and then switch it back after you have things working. Good luck