Media hub OS

I'm building a Media server out of scavenged old PC parts around my house. I have all the parts; I just don't know which operating system would suit my needs. I was hoping I could get Linux on it somehow but I'm not sure how easy it is to set something up a linux media server, considering I don't really know Linux that well yet. Plus, all of our other computers are running Windows 7 and Mac OSX :S

 

Suggestions?

It's much easier than you would think. I would recommend doing some googling. You can use something like XBMC and it will be really nice. Im at work but I will try to find some guides online to link later. :)