Can't get in my router any more. Help!

I have been using this wireless/wired router for 2 years for 3 pcs/laptops. It never had a problem, until recently I switched from DSL to cable modem.

My current router setting is a PPoE dial-up DSL setting, so I need to get in to reset it to cable model connection, which is a plug-in modem. But I can't access router's homepage.

However, my router can still assign IP to my PC and all other DHCP,DNS are correct, but I just can't PING it or access it, of course no Internet, 'cause my router is keeping trying the old DSL ISP once powered up.

My PC is a WindowsXP home with McAfee VirusScan. Windows firewall is not working at this time. My router is not a major brand, it's Billion.

Anybody had same expierence? Thanks!