Make sure you hardware is capable with MacOS, big problem these days with that is the drivers are not compatable. So, be careful, make sure ALL drivers and Motherboard will work. My friend did his 'hackinTosh' as he calls it, and he had one issue with the sound driver, so, save yourself a headache and do your background research.
I dual boot OS X and XP on my Apple machine using Boot Camp, but I'm not sure if you are talking about installing OS X on a non-Apple machine or you are talking about installing Vista on an Apple. I probably can't help with the former.
@Shadow, yeah, I already made sure. Like your friend, my sound card isn't compatible, but I don't mind ATM as I'm just testing it out before I Mac-ify my laptop, with which everything is compatible. This is just to make sure I can do it, to figure stuff out and the like. @Na, yeah, it's the former.