I could connect to the internet before when I had a static IP.

Now, my ISP changes the connection. I have to install PPPoE (which already provided by RH9.0) and obtain an IP dynamically via DHCP. However, after configuring by adsl-setup, running adsl-start could not get the connection to start (no errors but also no "connected" result). When I restarted, I saw "Bringing pp0 fail" (more or less). I have a Realtek PCI Fast Ethernet NIC.

(I can connect to the internet in WindowXP using PPPoE)

Please tell me what I can do to get the internet connection.
Thank you.

Some xDSL modems have a PPPoE client already in the modem's firmware.

Have you had a look at your modem to see if this is the case? It might save you some trouble.