I just removed Windows Vista from my computer by simply formatting the partition (as described here). But - as I guessed - this does not change anything with the Bootloader. So, when I start Windows, it still asks me if I want to boot Vista or XP.
So I tried to run
bootcfg on Windows XP to fix this problem, but it just holds the entry for Windows XP itself. Nothing about Windows Vista. So the bootloader in use is not the one from Windows XP.
Ok, I could run
fixmbr. But I also use GRUB as primary bootloader which will be removed from MBR with this. I could fix that again by booting from a Linux Live CD and running some commands from there. But is this really the one and only way to get rid of the Windows Vista bootloader?
For those who are confused now: Yes I use GRUB and a Windows bootloader. When I select Windows XP in GRUB the Windows bootloader appears and asks me if I want to start XP or Vista. Don't ask me why. It happened.