Check out my new Android app Find Your First Linux Distro.  That old PC has value, and you can revive it with Linux.  But out of the hundreds of Linux distros out there, which one should you start with?  Find Your First Linux Distro will help you decide based on the specs of your PC.

Find Your First Linux Distro is available for free at 
https://play.google.com/store/apps/details?id=com.jasonhsu.firstdistro

-- 
Jason Hsu <jhsu802701 at jasonhsu.com>