2003 to 2008 ad upgrade

i currently have 2 domains. 1 top level domain which holds the schema and DNM. And 1 thats hold the RID, infrastructure and PDC roles.
Currently all levels are 2003 native and i need to upgrade them to 2008.

can anyone please explain the best process, do i need a 2008 server in each domain?
should i do the holding domain first, do i also need to do the lower domain?

any advice welcome
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Krzysztof PytkoConnect With a Mentor Senior Active Directory EngineerCommented:
First of all, you need to prepare schema for new Domain Controller. Run in command-line

Netdom query fsmo

And identify Schema Master holder then on this DC run

Adprep32 /forestprep /rodcprep

And on each Infrastructure in each domain run

Adprep32 /domainprep /gpprep

Then you will be able to add new 2008 R2 DC in each domain.

For more info, please visit my blog at http://kpytko.wordpress.com
And look there fo "adding the first windows server 2008R2 within 2003 environment"

Adam BrownConnect With a Mentor Sr Solutions ArchitectCommented:
In order to upgrade the Functional level of each domain to 2008 you have to remove all Domain Controllers that are not Windows 2008 in that domain. To increase the functional level of the forest, you have to make sure there are no Domain Controllers that have a lower version than 2008 and all the Domains are at the appropriate functional level.

Basically, if you want to upgrade the functional level to 2008, you have to demote any domain controller that is not Windows 2008 or 2008 R2
Adam BrownConnect With a Mentor Sr Solutions ArchitectCommented:
So basically, you can do the following:
1. Install Windows 2008 Domain Controllers in each domain
2. Demote any Windows 2003 Domain controllers in your domains
3. Upgrade the functional level for each domain (doesn't matter which order)
4. Upgrade the functional level for the Forest.

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