Oh, it's not windows dude, that's a free linux OS called Ubuntu. You can dual-boot it with your current windows installation using their windows installer. http://wubi-installer.org (if .org doesn't work, try .com)
It'll let you download Ubuntu 10.10 and run both OSes side by side, once your ubuntu install is finished, google "MacBuntu" and download & extract that.....it requires some terminal command processing to get it up and running though.....