I did 'sudo apt-get update' and followed by many messages.
Final part of the error message says
I really really hope to update my ubuntu to 12.04. I already changed the download server to best server in US (because I live in Pennsylvania)
W: GPG error: http://ppa.launchpad.net hardy Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 04A38A9C1B826E04
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/dapper/universe/binary-amd64/Packages 404 Not Found [IP: 126.96.36.199 80]
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/dapper/main/binary-amd64/Packages 404 Not Found [IP: 188.8.131.52 80]
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/dapper/restricted/binary-amd64/Packages 404 Not Found [IP: 184.108.40.206 80]
W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/main/source/Sources 404 Not Found
W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/main/binary-amd64/Packages 404 Not Found
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/dapper-security/universe/source/Sources 404 Not Found [IP: 220.127.116.11 80]
W: Failed to fetch http://ppa.launchpad.net/ferramroberto/linuxfreedomlucid/ubuntu/dists/natty/main/source/Sources 404 Not Found
W: Failed to fetch http://ppa.launchpad.net/ferramroberto/linuxfreedomlucid/ubuntu/dists/natty/main/binary-amd64/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
Still not working. Is it the problem occurs because my Ubuntu 11.04 fails to find server or files?
Please someone help me with those GPG and following errors, regarding launchpad and others.
Thank you very much in advance