Trying to create 2nd partition on my macHD - help?

I'm using Disk Utility to create a 2nd partition on my MBP's Macintosh HD (500 GB capacity, which is ~130 GB full, the rest is free space, the new partition is 233 GB in size.) I've started the DU at about 11 a.m. - noon, now it's after 3 p.m., and DU says it modifying partition map, and it's still going, has the blue/white striped "barber pole" stripes since I clicked on "apply".

Why is it taking so long to create this new partition? How long is it supposed to take?

I started by highlighting the 500 GB "ST...." rather than the Macintosh HD icon in the left pane on my DU, clicked Partition, tried to name the new partition, but it wouldn't name it, and I clicked Apply.

Am I doing this properly? If I'm doing this the wrong way, how do I cancel the execution and start over?

If I'm going about this in the wrong way, could you please give me a step by step tut, please?

Thanks in advance.

EDIT - Found out how to exit the execution - went to File > Close (in DU menu), inserted my OS X install disc, restarted while holding down "C" key, opened Disk Utility from the OS X installer menu, and did the whole thing again, formatting the new partition as FAT (MS-DOS), bought a male to male USB cable, so I can plug the new partition into one of my Windows XP PC's and reformat it as NTFS.

More about this in another post elsewhere within Mac-Forms (another subforum).