I want to split my HD so I can use half of it to put all my music and the other half for all my other applications. When I open up Disk Utility and select my HD, it won't let me partition it. Why not? If this info helps, I'm running 10.2.6 on an iBook.
to partition your hard disk, you would have to erase it, you can't partition a formatted disk. you could back up everything, reformat your disk with two partitions and re-install your things, but it might be more trouble than it's worth.