I've thought of the name check too, but I'd prefer my method because:

Say your company's naming convention is to name all laptop computers MOB0000 through MOB9999 (MOB being Mobile). You could check if the computer logging on has MOB in it's computername or something, but chances are that people bringing in their own W9x laptop (e.g. Contractors etc) could also be using a computername with MOB in it. You would have to narrow down the check for the computername to f.e. a fixed length or something.

And now straying off-topic:

Say you did build a precise check if the computername is MOBxxxx: If you would also like to prevent privately owned or other outside laptops (with possible viruses, or who knows what on them) from logging on to the network, this check would prevent a lot, but the 'smart users' will be able to read the logon script, and change their computername to fit that of an 'allowed' PC.

(people who would like to get a free copy of licensed software that you roll out using the logon script could use this method.)

I know, it's a long shot, but eversince we had 1 user who figured out a password by reading the logon scripts, we always assume the worst. They say 'assumption is the mother of all f*ck-ups'.

Using a static file prevents most. Users with a private laptop or contractors etc could still use a computername of a PC of a person who is currently on holiday or something, but it would be a lot harder for them to do so.

Hold on:
My paranoide self is taking control; I'll stop this reply before I say you should shut down all servers to prevent unauthorised use !!