Verified answer

In my personal experience, the D-Link DI-524 is wonderfully reconfigurable. You can use it as just a switch, but even if you "turn off" its routing capabilities the wireless functions still work, so you can also use it as a separate wireless access point (which is what I'm doing), which, if your other router already has wireless access, means that you could run a cable to a different room to extend your wireless network. (Wireless networks that use the same SSID, pass-key, encryption type, and channel are 100% inter-operable without having to disconnect and reconnect.)

The first step after taking it out of the box is to plug a computer into the "LAN" side. (At this point, don't plug anything else into it.) We'll use this for configuration purposes. Launch another web browser and go to http://192.168.0.1/ (The login information should be username=admin and the password is blank, unless you've already changed them.) Click on the "Home" tab and then on the "LAN" button along the left-hand side. Change the IP Address to "192.168.0.2" and press the "Apply" button at the bottom of the page. A page will come up saying something like "Device is restarting" or "Saving Changes" and then eventually a "Cannot connect to server" page (or something like that). Type http://192.168.0.2/ into the address bar on the web browser and log in again. Click on the "Home" tab and now click on the button that says "DHCP". At the very top of the page you should see something like "DHCP Server" and then two radio buttons, one for enabled, one for disabled. Click on the "Disabled" radio button, and hit the "Apply" button at the bottom of the page. It will take you to a page that will say something like "Saving changes" and then take you back to the previous page. At this point, you can click on the "Wireless" button and do any configuration you want to on there. (If you don't want to use the wireless capabilities, feel free to just disable them outright, as this is much more secure.)

At this point, unplug the computer from the freshly disabled DI-524 and either reuse that cable or get another one and plug one end into a "LAN" port of the DI-524 and the other end into a "LAN" port on whatever other router you're using. (Don't plug anything into the "WAN" port of the DI-524 as it will not be useful for anything anymore.) At this point, you should be able to plug any computer into either device and they'll all talk to each other just as if they were all plugged into the same switch. Also, if you do decide to use the wireless capabilities, you'll find that any computer that is wirelessly connected to the DI-524 will operate exactly the way it would if it were wired into it or the other router.