Use Mac OS in virtual machine on Windows?
There are various (hacky) ways to do this 

eg http://www.lifehacker.com.au/2010/07/how-to-run-mac-os-x-in-virtualbox-on-windows/

But I would urge you to install VirtualBox in Mac OS X and then install Windows on that.  You can run Windows full screen.  It's going to be very quick and allow you the best of both worlds.  

Best of all VirtualBox is free and available here http://www.virtualbox.org/