How do I format a Apple Partition Map from GUID?

I just purchased a 1Tb Hard Drive which is formatted in Guid, but my G5 needs Apple Partition Map. I have told disk utilities to reformat but it keeps showing up as GUID instead of Apple Partition Map. This is causing my 10.5 Leopard disc from installing on the hard drive. Is there anything I can do or must I save this hard drive for a Mac Pro?