You can, but almost every update will break it, and when it is running it is not nearly as stable as on Apple Hardware, besides the fact that you cannot legally do it.
cos i know how to do it, my mate got so jealous of my awesome tiger-ness, that we figured ou thow to do it on PC...messege me if you want help (or on msn by i.m_not@hotmail.com, if that too is a ban😛 )
but it will run, in the bootcamp like manner windows runs on macs, it's just that it won't handle most applications because you're pulling tiger out of its native habitat (forgive the pun)