When manual Partitioning, create a Linux EXT2/EXT3 partition and a Linux Swap partition.

Reboot to the OS Selection menu. 
If your Linux root partition is a primary partition, you will see a Linux option.
If it is a logical partition, we will need to add it to the selection menu.
Go to Settings and Order Add Remove, Add, Partition.
Select the Linux EXT2/EXT3 partition and click on Toggle.
This will change the Boot Status from No to Yes.
Ok out and close Settings.
This should add the Linux option to the selection menu.

To install Red Hat.Reboot onto the Red Hat cd.Y
ou will come to a recommended partitioning. 
Ignore it and go to Manual Disk Druid.
Select the Linux partition you had created and click on Edit.
Include the mount point which is the forward slash "/".
You can also format it as either EXT2 or EXT3.
On the next screen or two, you will be asked to use GRUB.
GRUB is going to be place in the 'first sector of the boot partition'.