Computer modem question

[Evil ... Thy name is Orville Redenbacher!!]

Can I operate two wireless modems in the house?
I have a cable internet hooked up to a wireless modem.
I got a backup modem (same model and set up as my current system) at a yard sale over the weekend. Can I use it now as well?
The wireless set up we have is good, but doesn't cover the whole house. I want to run the other system to cover the rest of the house. Can I do it? Do I just need a cable to that room? Or do I need a computer as well?

 

[Walter Lippmann]

You can connect the two wireless routers with an ethernet cable. The spare one should have an uplink port. There are ways to connect the two wireless and have it appear as one network.

 

[Neutral Corner]

http://www.pcmag.com/article2/0,2817,2372811,00.asp