Problems setting up a linksys router.?

My old router broke, with the red diag led on. A friend from my office gave me a router to see if it works, a linksys WRT55AG without any installation cd or anything. As soon as I connected my ethernet cable I got internet working right away, however, my other computer connected to the router is not receiving wired internet (even though the computer is seen in the network although clicking it is unable to connect or access it). There are no password protections or anything between the computers. I try entering 192.168.1.1 on the main computer, but I get a connection was reset page (can't connect to it). I only seemed to be able to connect to it when I restart the router, reconnect the ethernet cable, and enter 192.168.1.1 quickly before the router is able to establish internet. Thus I am able to access the page, but when I try to make a change, it seems to save the changes (or not), establishes an internet connection on main computer, and again I can't connect to the page and my other computer still not having internet. How can I solve this?