Warning: I have never done this before, so this answer is entirely theoretical.
There are several solutions to the problem, which I detail below in increasing order of complexity.
1. Switch modem between bridged and non-bridged
This case is for when the modem in bridge mode is too simple-minded to do anything else
than pass packets between the inner and outer networks.
Unfortunately, this is the case with most routers, but I don't know about yours.
In this case the modem will never display its configuration page while in bridge mode
and the only way to return to non-bridged mode is to do a hard reset,
thus resetting the firmware to its original configuration.
When back in the original configuration, then one can connect the PC directly to the modem
to access the configuration page.
2. Direct connection
In the case when the modem can display its configuration page while in bridge mode,
the simplest solution is to run an Ethernet cable between the modem and your computer.
This will require your computer to have on the Ethernet cable NIC a static IP address such as 169.254.1.2, and for you to juggle between the two NICs.
So when you want to access the modem page, you will disable the wireless NIC and
enable the cable one.
3. Connect PC to both router and modem
This is for the case where the modem has wireless capability which still works in bridge mode.
One way is to change the PC IP address to a static IP address that will let it connect
to the modem, but not to the rest of the network or the Internet.
Another way is to assign the wireless NIC on the PC two simultaneous IP addresses
on both networks. Under Windows 7 this might requires that both addresses become static.
See these articles :
Multiple IP addresses – Windows 2008 R2 / Windows 7
(it mentions two KB patches that I believe are now incorporated in Windows 7).
How to Add/Assign Multiple IP Address in Vista/XP/2000/2003
Multiple IP address while first IP is given by DHCP (Windows 7)
4. Routing tables
The routing needs to be done in the router, which will then also work as bridge
between the two networks : 169.254.1.x and 192.168.0.
This requires a sophisticated firmware for the router. If the current firmware does not have
this capability, the alternate OpenWrt firmware has it and your router is mentioned
as supported in their list. Just a warning that flashing your router is always a dangerous
This configuration is to be done according to the documentation of your firmware.
Here is an example of such a configuration using OpenWrt.