Way to disable "ad hoc" wireless connection on domain without GPO

We are on a W2K3 corporate network. Everytime we image a new laptop with
XPsp2 and run sysprep, the built-in Windows wireless client setting for
"networks to access" defaults to "any available network".

Our problem is this includes "computer-to-computer" networks. For security
reasons, we do not want users making these ad hoc connections. They should
only be connecting to our AP's.

Is there a script, registry edit, or local security policy setting that will
lock down this setting/grey it out or, at least, set it back to "Access point
(infrastructure) networks only" after sysprep finishes? We do not wish to
use Group Policy or any other wireless interface (e.g. Intel, Dell, etc.).

I've searched long and hard for an answer to this with no luck. Any help or
suggestions would be appreciated.