Router user name and pass word not accept

Hello,
i had been using linksys wireless-g 2.4 ghz since long time, this time i have to change my apparte so i nee to change location now i have new password for internet and i am going to reconect this router but it not accept that old router user name and pass word also i think some one did use mistek setup in tis router so how i can acess in saide this router and creat wireless in my home pls
thank you for you cooperation
your regarded
joshi