VistaBootPRO is not a boot manager. What the application does is provide an easy to use interface to run the commands that bcdedit.exe and bootsect.exe (both being boot system programs built into Windows Vista).
To understand the boot processes of both Windows XP and Windows Vista in a dual boot scenario, one needs to first of all get to grips with the fact that both operating systems place their boot system files on the drive that is set as the first boot drive during installation of the OS's.
What this means in the case of two seperate drives is that if C: drive with XP installed on it was set as the first boot drive during installation of Vista you will find the folder Boot and the file bootmgr on the root of XP drive. You will need to show hidden files and folders in Folder Options and unhide protected operating system files to be able to see them.
If and when you migrate solely to Windows Vista, you will need to set your Vista drive as the first boot drive in your BIOS after you copy and paste those two items onto your Vista drive. Then run startup repair by booting from the Vista DVD and going to "Repair your Computer" at the bottom left of the "Install now" setup screen.
You will then be able to boot directly into Windows Vista without any boot menu at all and can replug your drive with XP on it and format it to remove Windows XP.
But to answer your question, yes, VistaBootPRO does work in Vista as it does in XP. It is really only intended to make changes to the Vista boot menu.
Hope that all makes sense
