Dandy, For Bootcamp to be activated you need to have a disk with single partition to start with. So if you have more than one partition, backup the data on the other partition and delete it so you have a single partition. ( you can delete and resize partitions without rebooting in Leopard) After having a single partition run the Bootcamp utility to do the needful.

Now fortunately there is a hack for everything including activating bootcamp on multiple partitions but this is unsupported. In case you would like to try then have a look at http://www.newartisans.com/blog_files/89eaccc5744b7474f4b95e35b8304847-3...
and
http://www.macosxhints.com/article.php?story=20071101065229169

-hth-