Need help with my router

Hello,

i found an old router lying around, now iv already got a router but my house is too big for it. i cant remove it because i have like 5 other pcs connected and i dont wanna mess around there. all i want to do is i want to configure the one that i found so that i can match the getways, mac IDs and stuff with my ADSL connection. but when i connect to my router it askd me for a username and password and i dnt know what the hell it is(not WEP)... isnt there some way i could hack into it or get the username and password or something?