How do I fix a download issue when updating? [duplicate]

Possible Duplicate:
How can I fix a 404 Error using a PPA?

For some reason every time I try to update by terminal, synaptic, and update manager I get this error message and I cannot update all the data I need.

W:Failed to fetch cdrom://Ubuntu-Netbook 10.04 _Lucid Lynx_ - Release i386 (20100429.4)/dists/lucid/main/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
, W:Failed to fetch cdrom://Ubuntu-Netbook 10.04 _Lucid Lynx_ - Release i386 (20100429.4)/dists/lucid/restricted/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
, W:Failed to fetch http://ppa.launchpad.net/canonical-dx-team/une/ubuntu/dists/natty/main/source/Sources  404  Not Found
, W:Failed to fetch http://ppa.launchpad.net/canonical-dx-team/une/ubuntu/dists/natty/main/binary-i386/Packages  404  Not Found
, W:Failed to fetch http://ppa.launchpad.net/lorenzo-carbonell/atareao/ubuntu/dists/natty/main/source/Sources  404  Not Found
, W:Failed to fetch http://ppa.launchpad.net/lorenzo-carbonell/atareao/ubuntu/dists/natty/main/binary-i386/Packages  404  Not Found
, W:Failed to fetch http://ppa.launchpad.net/meebey/ppa/ubuntu/dists/maverick/main/binary-i386/Packages  404  Not Found
, W:Failed to fetch http://ppa.launchpad.net/team-xbmc/ppa/ubuntu/dists/natty/main/source/Sources  404  Not Found
, W:Failed to fetch http://ppa.launchpad.net/team-xbmc/ppa/ubuntu/dists/natty/main/binary-i386/Packages  404  Not Found
, W:Failed to fetch http://ppa.launchpad.net/ubuntu-desktop/gnome3-builds/ubuntu/dists/natty/main/source/Sources  404  Not Found
, W:Failed to fetch http://ppa.launchpad.net/ubuntu-desktop/gnome3-builds/ubuntu/dists/natty/main/binary-i386/Packages  404  Not Found
, E:Some index files failed to download. They have been ignored, or old ones used instead.

Using Update Manager click the "Settings" button. This will open your Software Sources windows:

1. Untick the "CD-ROM" option - in my case it is "Ubuntu 10.10"
2. Go through the list and untick all your PPAs
3. Then click close
4. Check that you can now update successfully.

If you still cannot update then change your download mirror to another server: