Ok, I am a total novice at this, so bear with my ignorance--I have read a lot of the forums, but still can't quite figure it all out. I have a wireless router (Westell) from a DSL modem, which we connect computers to both wirelessly and by etherenet cables. The problem is the wireless signal doesn't reach upstairs to the other office area where we want to be able access to the network from. (huge old mill building with thick floors!) I got another wireless router (d-link DI-524) thinking I would connect the two routers by cable through the floor, but brought it home and realized it might be more complicated than that, and that I didn't even know what kind of cable to use. Can I even connect two routers like that? Or is there a better solution? Any help appreciated!

Take it back, and get a Wireless Access Point, not a wireless router. "If that [soiled bed] sheet is a [holy] manifestation, then I'm working on a miracle in my Jockey's!"

Yes, you will not need a wireless router. The wireless router would work, but you would not be using any of the routing features. The access point you buy must have the ability to act as a client in a WLAN environment. I have never personally tried a setup similar to this, but you should just have to configure the AP with the SSID of the router. I am not sure how many switch ports AP's are coming with anymore, it used to be only one port. If that is still the case, you will have to buy another switch, connect your computers to this switch, then connect this switch to the single switch port on the AP. The other thing I would research before you buy anything is whether or not the AP configured in client mode will work with the Westell router/DSL modem.

You must ensure if you do use the router you disable the DHCP server in it, and NOT to connect it to the other router using the WAN internet port. "If that [soiled bed] sheet is a [holy] manifestation, then I'm working on a miracle in my Jockey's!"

You also may want to look into just getting a wireless repeater/range expander. This would save you a lot of problems. no configuring needed with a repeater/ range expander.