hello sir,
in ubuntu 9.04 while am doing system->updatemanager->settings am getting error like
Could not download all repository indexes

The repository may no longer be available or could not be contacted because of network problems. If available an older version of the failed index will be used. Otherwise the repository will be ignored. Check your network connection and ensure the repository address in the preferences is correct.
Failed to fetch http://security.ubuntu.com/ubuntu/di...-i386/Packages 404 Not Found [IP: 91.189.92.181 80]
Failed to fetch http://security.ubuntu.com/ubuntu/di...-i386/Packages 404 Not Found [IP: 91.189.92.181 80]
Failed to fetch http://security.ubuntu.com/ubuntu/di...-i386/Packages 404 Not Found [IP: 91.189.92.181 80]
Failed to fetch http://security.ubuntu.com/ubuntu/di...-i386/Packages 404 Not Found [IP: 91.189.92.181 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/dis...-i386/Packages 404 Not Found [IP: 91.189.92.202 80]
Some index files failed to download, they have been ignored, or old ones used instead.
so where i did the mistakes please give me the reply

You chose a version that is no longer formally supported (and hasn't been for some time). You did something that needed support. It didn't work.

Care to make your own guess as to why that didn't work?

Here is a timeline of whuch versions are supported.

In addition, going for an old and/or soon to be unsupported version, without a specific good reason for doing that, is usually a suspect move.

9.04 is no longer supported. The current long term release is 12.04 and the regular release is 13.04. You should install a more current version

http://security.ubuntu.com/ubuntu/dists/ jaunty is no longer there

Have Fun Upgrading.
As well as your data, backup your hidden profiles
ls -a to see them all.

Larry Keenan