El Torito: Booting the final image in the test machine

To all experts, hope you can help me with this.

After creating the final image by following the xpe documentation
about creating a bootable cd.

What I did:
- Setup the test machine in 2 partition; 1 is 5GB (FAT) and other
remaining of the hard disk.
- Boot the bootable-CD that contains the image after POSTFBA

The Result:
- Successfully launch XPe, running properly, but the disk space is
low; when i check it on my computer explorer, the partition became 3:
1p is 650 which same size of CD, 2p is 5GB - 650MB and 3p is the
remaining space of the hard disk.

Here's my question:
- Why does it create another partition which same size of CD?
- When restart after the result, removing the bootable-CD will not
boot to XPe. Does the content of bootable-CD that contains in image
was copy to that partition which is 650MB?

Is there something i miss? Pls. help...thanks in advance...sori 4 my
english.