Help installing windows vista in a dual boot enviroment

I currently have 3 partitions on my computer, one for xp pro, one for vista enterprise and one for data. I would like to get rid of the xp pro partition and install windows vista business instead of enterprise which I currently have. In the end, I want to have two partitions, one for vista business and one for data. I also want to add the 20 GB I alloted to xp pro back to the data partition. I used partition magic 8 to set up the partitions in the first place. What is the best way of accomplishing all of this? I was thinking maybe format the xp pro partition and then allocate that space using partition magic to the data partition. I have no clue on what to do about installing business over enterprise. Thanks