Thank you very much for your reply to help me. I actually tried to put that command ifup eth0 in /etc/rc.local and it seems work one time and another time it doesn't. I don't know why it is giving me a hard time. Everytime I want to use wireless, I have to run that command again at root to get the ip address. I have never had any trouble like this with other distros.

Oh, I am running on DSL witch kernel of 2.4.XX. I am running on runlevel 5 for gui. I don't know what to do with it now. Thanks a lot.