I just installed XP Pro on my Sony Vaio that came with Vista Home Premium preinstalled as a dual boot setup, according to your guide. XP booted fine the first time, and after i installed VistaBootPro Vista booted fine. But, now if I select XP, it says:
Windows failed to start....blahblahblah....
Info: The selected entry could not be loaded because the application is missing or corrupt.
I tried repairing the XP installing from the XP disc with fixboot, and got XP to boot again but of course vista disappeared.