Trying to dual boot IBM laptop

I have an IBM Thinkpad 1 Ghz PIII, I want to install Windows 98 as a dual boot operating system, it has XP Pro now. I have been trying to use Partition Magic to partion the hard drive and XP or something has the whole 15 gig allocated and shown as used in the drive properties. How can I get the system to recognize that the drive actually has 12 gig free that I could partition part of?