Deny DHCP access

Is it possible to deny a Dynamically assigned address to a specific MAC
Address, using the Windows Server 2003 DHCP server? We have many remote
offices, and clients will bring thier unauthorized laptops in (obvious
security problem) and the employees will not stop them from plugging in. I
know that employee security training is the best option, but in lieu of that?

I am also needing a solution for this. I am surprised that Microsoft
has not provided an easier way to do this with their product.
Our situation is unique...a bit different.
We have 3 devices on our network which MUST pickup their addresses via
BOOTP from a very old UNIX server on our network (this setup is
currently required). We need our Win2K3 DHCP server to ignore their
BOOTP requests.
I have not seen an easy way to do this yet. I know that we can reserve
all of the addresses in our scope, but that will be a painful process,
because we would have to reserve IP's for over 40 PCs (their MAC
addresses).
Come on MVP's! I know you can give some assistance here. We do not want
to assign bogus addresses to these devices. This is a car dealership,
and we have to work with GM, Toyota & another integration company. We
do not manage these devices. This is why we can't just redesign the
network at present.
Any help would be appreciated.

Thanks.