adprep and forestprep for 2003 R2 HELP!!

I have also posted this on the active directory group but I will post it here
too.

I have an existing 2003 server domain and I am trying to add a brand new
2003 R2 server as a domain controller. However when I run dcpromo on the new
machine it says I need to run adprep forestprep and domainprep.

I take the R2 CD and run adprep /forestprep and adprep /domainprep on my
primary domain controller and it tells me that the information has already
been prepared/updated.

I'm totally stuck. Does anyone have any idea what I need to do?