go to
www.linuxiso.org. they have links to most all distros you can d/l.
if you want something usful and be able to learn at the same time try building a router from your old box. go to
www.clarkconnect.org or
www.freesco.org.
you can d/l all the software needed to build a router and you have something to learn with.
i use a clarkconnect and can't imagine being without it now.