Fedora Core 5 is currently EOL – it’s not supported any more.  As a result, you might find you can’t use yum to install packages any more – you get an error message about this file not existing:

http://download.fedora.redhat.com/pub/fedora/linux/core/5/i386/os/repodata/repomd.xml

This is because the repositories that yum uses aren’t there anymore.  However you can modify the repositories in /etc/yum/repos.d/ and add these to fix the problem:

http://archive.fedoraproject.org/pub/archive/fedora/linux/core/6/i386/os/
http://archive.fedoraproject.org/pub/archive/fedora/linux/core/6/i386/debug/
http://archive.fedoraproject.org/pub/archive/fedora/linux/core/6/source/SRPMS/

http://archive.fedoraproject.org/pub/archive/fedora/linux/core/updates/6/i386/
http://archive.fedoraproject.org/pub/archive/fedora/linux/core/updates/6/i386/debug/
http://archive.fedoraproject.org/pub/archive/fedora/linux/core/updates/6/SRPMS/

http://archive.fedoraproject.org/pub/archive/fedora/linux/extras/6/i386/

An example change would be to the /etc/yum/repos.d/fedora-core.repo file:

[core]
name=Fedora Core $releasever – $basearch
#baseurl=http://download.fedora.redhat.com/pub/fedora/linux/core/$releasever/$basearch/os/
baseurl=http://archive.fedoraproject.org/pub/archive/fedora/linux/core/5/i386/os/
[core]
name=Fedora Core $releasever - $basearch
baseurl=http://archive.fedoraproject.org/pub/archive/fedora/linux/core/5/i386/os/