What to do with an old PC?

Sorry if this isn't the right forum but I didn't exactly know where to put it.

Well I've recently upgraded my computer and now I have an entire extra computer lying around. I've been trying to think of some good ideas on how to use it but I'd like some opinions and more ideas.

Specs:

i3 550 
Amd Radeon 5670 gpu. Can't get anymore specific, it's old but it still performs decently. 
An MSI mobo 
4 gigs of 1333 ram

Play around with various Linux distro's, make it a torrent box, make it a media server, sell it, give it to a poor student in your neighbourhood that needs a pc for school. Heap of options.

You could try to sell it by parting it out? Nas, small game server, PF sense box. Just some ideas.