So the first problem I saw was it seems you have the definitions of external and internal IPs confused. But that shouldn't keep us from helping you. :)

So First off, you cannot access your router through your modem by using 192.168.0.1 as this is assigned to the router by itself. The clients will be able to access it in this way, but not the modem, or anything connected to the modem, because it doesn't have a DHCP entry with that address.

That aside, the reason you might not see the configuration screen for your router is because the port is locked down. As far as the router knows, your computer is a random computer from the internet, as such the firewall blocks most ports from connecting. It could also be that your port 80 is being used by a different service.

In any case, the only way to access your router would be to open port 80 in port forwarding settings and have it point to 192.168.0.1 (in router settings). This should do what you want. Here is a quick guide.

• Open your router's configuration
• Click Advanced Settings on the left hand side
• Click NAT
• Click the Add button
• Select the Custom Service radio button
• In the Name field type something like Router Config
• Enter 192.168.1.2 as the server IP.
• For all External and Internal port fields type 80.
• Click apply and save.

Just note, I was unable to find the exact model you specified as your router. So the settings or names may change. Regardless you are looking for NAT or Virtual servers as a setting option. Most of the values should be the same from there.

You should now be able to access your router from your desktop connected to the modem. (If not try restarting the router)

EDIT:

The method above should allow you to see the configuration screen from the clients of the modem. If NAT is unavailable, you need the Virtual Server option.

So you want to share files between systems... This procedure becomes more complicated at this point...

First thing you will need is a FTP server hosted by one of your systems. You can find many a many tutorial online. For Windows, Filezilla works for a server, for Linux systems you have to be a bit more in depth.

I won't post a guide on setting one up, due to there being many ways and systems across your network. And lack of information on a potential server.

However, once you get a FTP server running on your "server" you just have to port forward it with the same method above. However changing the port from 80 to 21 (if you keep the default).

Hope this Helps!