.
Specifications, please. Include model and speeds. If the system is still running, use
SIW or
something like it to perform an in-depth hardware profile.
CPU:
GPU:
RAM:
NIC:
OTHER misc. parts, like add-in cards:
Then, what might you want to do with it? Learning linux is one good option.
Build a NAS ..?
2ndary media player ..?
2ndary web-surf & email ..?
Dedicated ("headless") torrent server ..?
Killer firewall/security for your internets ..?
Need to evaluate tradeoffs, such as system capability/resources/power and amount of electricity/heat used/generated for what service(s) it could provide.
If you need the case, you should be able to repurpose a really old useless one that you can obtain free somehow. For a PSU, depending on what you attempt, you may be able to get by with a 250 or 300 Watt.