There have been reports that the Boot Camp Assistant has trouble partitioning your hard disk since the 10.5.2 update. In some cases the Assistant just freezes you Mac in some other cases it causes kernel panics. In my case the Mac froze and the BC Assistant just didn't create the partition that I wanted. Then I came across a thread in a Mac forum that someone successfully partitioned his drive after reinstalling Leopard - that gave me an idea, which was to try restoring my SuperDuper! backup for the first time ever. Doing that would get rid of any defragmentation also, I thought. So booting from the install DVD and launching disk utility, I mounted the bootable sparse image disk that SuperDuper! created and started restoring the image to my Macintosh HD (note: the free version can clone your whole disk). I was amazed how fast the restore process was and after about 45mins I booted up my "old" restored OS X. Amazingly, Boot Camp Assistant was now able to create the Boot Camp partition and I was able to install Windows on my Macbook - I guess the problem with Boot Camp in some cases is, that the Assistant fails to move some files on the Macintosh HD to create the partition. If you absolutely need Windows (yes for some specific programs people need Boot Camp) and have trouble installing it this might be an easy safe way to do so.