If it's a new drive, without any version of Windows XP installed, boot with the Window XP
CD (if your System Setup/BIOS doesn't have the CD Drive as the first drive in the boot
sequence, on boot enter System Setup and change the boot order of the drives until the CD
Rom drive is the first in sequence, then select the option to exit and save settings).
After booting with the Windows XP CD the install will begin, when you get to the screen
where it asks where you want the install, press the ESC key, and you will see all of the
options for formatting and partitioning.
The above is ONLY for a NEW (clean) install. If you already have Windows XP and your
software installed: The Windows XP native partitioning utility does not allow for
partitioning without losing your data (partitioning on the fly). If you want to
partition, or change the size of existing partitions, without losing data, you would have
to use a third party partitioning utility like Partition Magic:
http://www.symantec.com/partitionmagic/