Bootcamp help

I am trying to install Vista on my Macbook Pro with Bootcamp but it keeps on telling me that "The startup disk cannot be partitioned or restored to a single partition." However my hard drive is not partitoned.

I am ready to give up and do a fresh install but hopefully there might be a way to correct this problem.

if you have a program like iDefrag or Techtool Pro 4 you can do a disk optimization and it will defrag your hard drive and then you will be able to format the partition, the same thing has happened to me twice.