Local Groups LOST after Sysprep :-(

Hello and thanks for reading this:

My goal is to have one master image, for both our laptop force, and
our LAN-connected desktop folks. I use domain groups *AND* local
groups *simultaneously* to control who has access to particular
folders on the NTFS C:

e.g. mydomain\MSfront-page & localmachine\MSfront-page gets access to
the MS Front Page folder on the C:. When setting up a laptop, I add
the user to the appropriate local groups. When setting up a lan user,
I just add that domain\userid to the appropriate domain groups, and
when the user logs in, he or she immediately gets access to the proper
folders on the C:

The Problem:
After sysprep strips the sid, the imaged pc shows a bunch of numbers,
instead of the local group name (e.g. localmachine\MSfront-page).

The Question:
What is the best way for me to prevent unauthorized Laptop users from
accessing folders I want on the C: The laptop users do not
authenticate to my domain, so I can't use the domain groups to control
access. I don't want to start right clicking on particular folders
after restoring the image to recreate all the permissions which were
lost by sysprep.

Any, and all ideas are very much welcome and appreciated.

Thanks!
mikeweb@curtiscirc.com