uninstall Vista from a dual boot

2 physical drives C: and D:

Windows XP Media Center on C:

Windows Vista installed on D:

I want to remove the Vista install, but not sure what tools to use to ensure
that my MBR, boot.ini etc do not become corrupted in the process. It will
not let me delete the Vista folder even when I am booted into XP, and when I
looked at my boot.ini to see if I needed to edit, it referred me to
bcdedit.exe. Not sure how to manipulate this.

I don't need to save anything from the Vista install as it was just for a
test drive, I just want to get my PC back to a straight XP MC computer.