Has anyone installed Windows 8 without Windows 7 already installed? I currently have Release Preview installed and have a copy of XP that I used with Snow Leopard on my old MacBook, but since I am now running Mountain Lion, XP is no longer supported. Is it possible to use the Release Preview as a previous version of Windows and upgrade from there? This looks somewhat promising http://pcsupport.about.com/od/windows-8/a/clean-install-windows-8-upgrade.htm but I don't want to go and drop $40 on the upgrade only to find out that it doesn't work and then have to pay more for a full version in addition to the upgrade. Has anyone done this?