Problems with partitioning for RH workstation 6.3 -x86_64 dvd

Fri Dec 7 16:45:30 UTC 2012

I have windows 7 installed on the first half of the system disk.

sad1 vfat
sda2  ntfs
sda3  ntfs   476739 MB
sda4  unknown  486739 MB

I want to install RH 6.3 on the unknown portion of the disk, splitting that
up into /, /tmp, /var, /usr, /usr/local and /research.

I don't seem to be able to partition the sda4 portion.  How do I do this
using the 6.3 dvd.