From what I've read it can be done but some of the hardware in your PC might not work or at least not work the way you want them to. The graphic card would be the main issue i would think. I think OSX is picky on what hardware it likes to play with.
My brother is replacing Vista and installing Ubuntu Linux on his PC tonight and I'm curious how that will go.
Ubuntu (Linux) on a PC, from what I've read, might be something to look into. It is free and apparently gives you a lot of control over how you want it to look and work. The screen-shot's I've seen on the net makes it look just like Windows or OSX. I've read alot of good stuff about it. Since it is free it wouldn't hurt to give it a shot. I was thinking of trying it out on my old PC to see what it is like if my brother seems to like it.