[syslinux] Mount Hard Drive Once Booted?

[Stoneguard]

Hi. I am new to syslinux and have been searching for days for a solution to
an issue. I feel I am missing something simple.
 
I have a syslinux USB drive made from HP (nice utility they have). It mounts
an A: DOS drive and mounts the USB flash drive as C:. However, I also need
the actual system hard drive mounted. How do I do that? Is it possible?
 
-Phil