winnt.sif file confusion; how to NOT format the target drive

Archived from groups: microsoft.public.windowsxp.configuration_manage (More info?)

Hi, I'm working on an unattended XPinstall CD but I'm unclear about
the Drive and Partition it's going to install itself in when using the
winnt.sif file parameters.
The circumstance:
I have one drive on a laptop split into two FAT32 partitions; C: (5gig
for OS and programs) and D: 35gig (for data). I don't want to wipe out
my data partition by repartioning the whole drive accidentally with a
misplaced line in the winnt.sif file. I set the line;
Repartition=no
to prevent that- assuming I interpreted the instructions correctly. I
also set the line;
AutoPartition=1
with the expectation that the unattended install would find the first
partition it came to (I guess that's C feel it up to see if windows
was already installed, and go to town.
The Problem: (sorry, challenge,..)
I made an ISO and fed it to MS Virtual Machine (very cool) but the
simulation stops the install at the point where XP gives you the
option to install to C: or reformat to NTFS or a couple other things
but it's not unattended, you have to tell it what to do.
So what am I doing wrong? I have to boot to DOS and wipe the 5 gig
partition (which currently has XP installed on it) and then things
will go along unattendedly? Thanks for your time.