Suggestions for Free Low-End PC

So I was heading home from the grocery store and found a PC on the curb waiting to be thrown in the trash. I then immediately picked it up and carried it awkwardly on the bus and then back home. Surprisingly it boots just fine and although it operates rather sluggishly due to a very cluttered Windows Vista I found no issues with the hardware. Another strange thing was the owners did not wipe their accounts and data. 

Anyways, the PC is an HP Pavilion Media Center m8200n. A rather low end system but it was free so how can I complain. The graphics card(Nvidia GeForce 6150 SE) is pretty much abysmal from what I've searched and a ~$50 investment into a older dedicated GPU would help tremendously.

Specs: http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01151028&tmp_task=prodinfoCategory&cc=us&dlc=en&lc=en&product=3548185#N368

Now that I've explained how I found the PC and a brief description of it, the real issue is what to do with it? I already have a high end gaming system(although gaming on this free PC would be severely limited to certain games and settings) and I have a Raspberry Pi which is my HTPC with XBMC. The only suggestions I can come up with is either use it as a server / cloud storage or replace it with the Raspberry Pi(as this system may have more power especially if I purchase a GPU). Then once replaced I can use the Raspberry Pi for other DIY projects I may have an interest in. 

Please enlighten me with any interesting/useful ideas I can do with this new toy. 

Thanks!

If it has a SATA controller, move it to a more appropriate case and make a NAS or put a NIC in there and make a dedicated router out of it. Otherwise you could play touhou on it and manage 60 fps I reckon. lol

it would be ok media / xbmc device with low end GPU... like you said and more drives if you have stored media 

or maybe nas media server?