i'm not familiar with vista but you need to find a way to manually install the XBCD driver over the microsoft one.
If you can find the device in Device Manager right click and click the drivers tab. In the hardware update wizard the default is Install software automatically, but you want INSTALL FROM A LIST OR SPECIFIC LOCATION (ADVANCED) and from there click DON'T SEARCH. I WILL CHOOSE THE DRIVER TO INSTALL and then XBCD should be on the list to choose.
The thing is if you let it update the driver automatically it will always use the Microsoft, find a way to update the drive MANUALLY or from a list and then you will be able to choose XBCD and then it will work when u go into the XBCD configuration