It seems like that Red Hat has changed the location for the Fedora Core 1 updates.

Here the updated /etc/yum.conf:

[main]
cachedir=/var/cache/yum
debuglevel=2
logfile=/var/log/yum.log
pkgpolicy=newest
distroverpkg=fedora-release
tolerant=1
exactarch=1

[base]
name=Fedora Core 1 - i386 - Base
baseurl=http://download.fedora.us/fedora/fedora/1/i386/yum/os/

[updates-released]
name=Fedora Core 1 - i386 - Released Updates
baseurl=http://download.fedora.redhat.com/pub/fedora/linux/core/updates/1/i386/
 
[updates-testing]
name=Fedora Core 1 - i386 - Unreleased Updates
baseurl=http://download.fedora.redhat.com/pub/fedora/linux/core/updates/testing/1/i386/

Up2date users

Here the yum sources for /etc/sysconfig/rhn/sources:

yum fedora-core-1 http://download.fedora.us/fedora/fedora/1/i386/yum/os
yum updates-released http://download.fedora.redhat.com/pub/fedora/linux/core/updates/1/i386
yum updates-testing http://download.fedora.redhat.com/pub/fedora/linux/core/updates/testing/1/i386