It really depends what you use it for. You got gaming computers that run servers on games, like my friend has a garry's mod server on his own personal gaming computer. Or you could do unRAID (I would do research for that) for a server, it allows you to have Virtual Machines. LinusTechTips did a video on that a while back. Personally I think if the server is small and you have a computer that can handle the server, yes you can run a server on a regular computer, I just hear lots of ram is needed. But again, it all depends on what the server is for.