nope, XP uses MBR, Vista uses BCD
If you want to muck around with the boot.ini use EasyBCD
(Must be installed under Vista, does not work under XP)
With this progrramme you can alter and set the boot.ini to either boot into XP or Vista by default (if dual booting), change timeout etc for OS choice yada yada yada.
I think that's what you were asking, if not explain a little more what you are trying to achieve.