If the computers you are setting up are XP Pro:
Knowledge base article 291586 tells you how to log in as
an administrator before running sysprep, create a "Test"
account with all the customized settings, then copy these
settings to the "Default" user account, so that when your
user runs the Windows Setup, and puts in "John Doe" as
their user name, that should be the only account available
for log in.
If the computers you are setting up are XP Home Edition:
I had the same issue, and ended up having to tell the end-
user with instructions to log in to the account I created
("User") and then give them instructions on how to change
their account name. This was because of the limited time
I had to implement this.
But, I believe if you use sysprep.ini - you can create
your own custom application that you set up to run in the
[GuiRunOnce] section. There is a tool that helps you
create your sysprep.ini to create unattended
installations, or create answer files for such settings.
I think it is the Setup Manager. Found in the support.cab
on the Windows XP Professional CD. Companies like Dell,
and IBM buy the OPK for OEMs, and there is more tools
available to them.
I hope this kind of helps, or points you in the right
directions.
Lynn