Can't get WRT54GX2 to connect

Hi, new to networking but hooked a Linksys WRT54GX2 router to a WinXP computer and put a wireless network card in the other. I don't see any problems with the wireless network card, it even shows my neighbors LAN (but I didn't check into hacking it and don't want to). The dsl modem works fine when the router isn't hooked up, but when the router is hooked in, there is no connection at all, and the other computer doesn't pick up a signal from it, like the router isn't working. (I have to disconnect the router and take it out of the system for the modem to connect to the internet, it won't when the router is connected in the system). But some of the lights on the front of the router light up, such as the network cable I have connected, it sees if it's 1 or 2 or 4 and lights the corresponding light on the front of the router.

The router came with a setup cd, I reset the router's settings from the button on the router back and then ran the setup cd. After a point it says to enter a username and password. I leave the username field blank and enter "admin" (without the quotes) as the password, like the manual tells me to. But when I do it just takes me back to this window, like something isn't correct with the information I entered, and asks me to enter this information again. It won't go any further once I get to this point.

Any solutions or things I can try?