You need to set one to bridge mode. Here is a little about bridge mode.
Wireless Bridge - What is Bridging Mode in Wi-Fi Networking?

You'll need to find out if and how your routers support bridge mode.

You could also flash your current router with DD-WRT a free Linux-based firmware for several wireless routers, most notably the Linksys WRT54G (including the WRT54GL and WRT54GS). It is licensed under the GNU General Public License version 2.
DD-WRT - Wikipedia, the free encyclopedia
DD-WRT :: News
Linksys WRT54G series - Wikipedia, the free encyclopedia