Do a quick format with XP it will be just about as fast. I would say no, your best bet is just to format the disk while you are installing. XP should be installed first - the windows boot loader will be installed on the Boot sector of the first partition of the first physical drive for all OS's - no matter what disk the OS is installed on. The newer version of windows should always be installed second, since it will know how to manage the boot loader of the old, but the old won't know how the new boot loader works, and the boot loader of Vista/7.0 is completely different from the XP boot loader, as is their partition table. That's why you don't want to format with 7.0 for XP to load.