Buying and installing windows vista on a ubuntu computer

How would I go about buying and installing windows vista on a ubuntu computer?

Unfortunately ... no you cant upgrade from linux to vista, but it is very straight forward, and surprisingly fast to install vista. when you insert the vista DVD, reboot the pc and make sure that your pc is set to read the dvd-rom drive on boot (this option will more than likely be in the bios settings, although some manufacturers let you do it from windows). vista will auto detect your current operating system, and ask you if you want to keep it or remove it, you make the choice and in about 20 mins you're up and running :)