Big XP rollout upgrading from NT4 to XP but without qualifying CD

Hello,

I have a big (several thousand clients) rollout of XP to carry out.
Each machine is a Dell and came supplied with either NT4 Workstation
or 2000 Professional. My boss has purchased a large quantity of Retail
XP Professional Upgrade licences.

We will be wiping the disks before installation due to the pre-boot
process we use (On Command CCM). Unfortunately neither the Dell NT4 or
2000 recovery CDs work as qualifying media. We have asked Microsoft
for suggestions but they haven't come up with anything. We could use a
proper retail CD as the qualifying product, but the clients are spread
over approximately 250 sites so this isn't ideal either.

Does anybody know a way to get around this? Perhaps with a setting in
the unattend.txt file? I have searched the Web and newsgroups but
haven't found a solution.

Thanks,
Martin.