Problemas com linux 11.04

Gente estou com problemas , a minha central de programas nao esta pegando , e quando vou atualizar na Synaptic aparece o seguinte erro .. Ninguem me ajudou ja fiz varios topicos me ajudem por favor


Falhou ao buscar cdrom://Megalinux Diamante _Natty Narwhal_ - Release i386 (20110427.1)/dists/natty/main/binary-i386/Packages Por favor, use o apt-cdrom para fazer com que este CD-ROM seja reconhecido pelo APT. O apt-get update não pode ser usado para adicionar novos CD-ROMs
Falhou ao buscar cdrom://Megalinux Diamante _Natty Narwhal_ - Release i386 (20110427.1)/dists/natty/restricted/binary-i386/Packages Por favor, use o apt-cdrom para fazer com que este CD-ROM seja reconhecido pelo APT. O apt-get update não pode ser usado para adicionar novos CD-ROMs
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty/restricted/source/Sources 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty/main/source/Sources 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty/multiverse/source/Sources 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty/universe/source/Sources 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty/restricted/binary-i386/Packages 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty/main/binary-i386/Packages 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty/multiverse/binary-i386/Packages 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty/universe/binary-i386/Packages 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-backports/main/source/Sources 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-backports/restricted/source/Sources 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-backports/universe/source/Sources 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-backports/multiverse/source/Sources 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-backports/main/binary-i386/Packages 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-backports/restricted/binary-i386/Packages 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-backports/universe/binary-i386/Packages 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-backports/multiverse/binary-i386/Packages 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-updates/restricted/source/Sources 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-updates/main/source/Sources 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-updates/multiverse/source/Sources 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-updates/universe/source/Sources 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-updates/restricted/binary-i386/Packages 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-updates/main/binary-i386/Packages 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-updates/multiverse/binary-i386/Packages 404 Not Found
Falhou ao buscar http://br.archive.ubuntu.com/ubuntu/dists/natty-updates/universe/binary-i386/Packages 404 Not Found
Falhou ao buscar http://extras.ubuntu.com/ubuntu/dists/natty/main/source/Sources 404 Not Found
Falhou ao buscar http://extras.ubuntu.com/ubuntu/dists/natty/main/binary-i386/Packages 404 Not Found
Falhou ao buscar http://security.ubuntu.com/ubuntu/dists/natty-security/restricted/source/Sources 404 Not Found [IP: 91.189.92.190 80]
Falhou ao buscar http://security.ubuntu.com/ubuntu/dists/natty-security/main/source/Sources 404 Not Found [IP: 91.189.92.190 80]
Falhou ao buscar http://security.ubuntu.com/ubuntu/dists/natty-security/multiverse/source/Sources 404 Not Found [IP: 91.189.92.190 80]
Falhou ao buscar http://security.ubuntu.com/ubuntu/dists/natty-security/universe/source/Sources 404 Not Found [IP: 91.189.92.190 80]
Falhou ao buscar http://security.ubuntu.com/ubuntu/dists/natty-security/restricted/binary-i386/Packages 404 Not Found [IP: 91.189.92.190 80]
Falhou ao buscar http://security.ubuntu.com/ubuntu/dists/natty-security/main/binary-i386/Packages 404 Not Found [IP: 91.189.92.190 80]
Falhou ao buscar http://security.ubuntu.com/ubuntu/dists/natty-security/multiverse/binary-i386/Packages 404 Not Found [IP: 91.189.92.190 80]
Falhou ao buscar http://security.ubuntu.com/ubuntu/dists/natty-security/universe/binary-i386/Packages 404 Not Found [IP: 91.189.92.190 80]
Alguns arquivos index falharam ao ser baixados. Eles foram ignorados, ou cópias antigas são usadas ao invés.

Qual a versão do Ubuntu que está usando?

Ubuntu-11.04 não tem suporte desde outubro 2012.
Instale ubuntu-12.04-lts

Use repositórios "arquive" ou atualize a sua distro que ja e sem suporte.