I started this awhile ago and I just want to get the information posted for my reference. I had a Windows 2008 x32 (DCOLD) server acting as my primary domain controller and DNS. I wanted to introduce a new Windows 2008 R2 x64 server and promote it to take over all the roles of DCOLD.

Windows 2008 DC (DCOLD)

Install Windows 2008 R2 x64 (DCNEW).
Ensure that network settings are configured to support DCOLD (Use DCOLD as DNS, make sure network domain name is set to DCOLD domain name).
Join DCOLD domain as a member server.

DCOLD (Windows 2008 32bit):
Copy the support\adprep directory from the installation source iso.
Run adprep.exe /forestprep

This did not work because I initially copied adprep from the 32bit source.
I got the following message”

Forest-wide information has already been updated.
Adprep did not attempt to rerun this operation.

Solution (You need to use adprep from the 64bit installation source.):
I had to copy the support/adprep directory from the Windows 2008 R2 CD, and run the following

adprep32.exe /forestprep

Install Windows 2008R2
Configure name/network, and bring into domain.
Run dcpromo.

Transfer roles 5 roles to DCNEW:

Schema Master
RID Master
Domain Naming Master
Infrastructure Role
PDC Emulator

This is a very basic outline, and there are several clean up steps that need to occur after this if I wanted to demote and remove DCOLD.