You just got a new PC with Windows Vista pre-installed, and you want to dual-boot Windows XP for old programs – or just nostalgia’s sake. You already know how to dual-boot Windows Vista on your XP machine, but you can also set up Windows XP to boot from a separate partition on your Vista PC.
First you’ll need to repartition your hard drive inside Vista, install Windows XP on that new partition, and then use previously-mentioned VistaBootPro to set up your bootloader. A poster at the ProNetworks forum has the detailed rundown, along with helpful screenshots. —Gina Trapani
From Lifehacker