I'm trying to get into Ubuntu and have just installed it from a disk I had lying around. The version is 7.04, and I would like to upgrade to a more recent version.

I've tried using update manager, but I get an error message that it "Could not download all repository indexes" with a list of maybe 20+ websites. Most of these start with security.ubuntu.com or us.archive.ubuntu.com.

Can anyone help me?