moving from a NT4 domain\exchange 5.5 to win2003\exchange 2007

In Windows 2000/2003 there are no pdc's and bdc's anymore thats right. You will promote the server to a domain controller by running dcpromo. But still one of your DC's plays a "PDC role" to support older clients.

Afaik a direct upgrade from 5.5 to 2007 is not possible. You should find all information you will need here:

http://www.microsoft.com/technet/prodtechnol/exchange/2003/upgrade.mspx

Have a look at this also:

http://technet.microsoft.com/en-us/library/a313c016-0e51-466e-a3de-953e1e0d347d.aspx

Under the second "Important"-section its clearly stated that you first have to migrate to Exchange 2000 or 2003 before moving on to 2007.

You need to get off Exchange 5.5 first.
That means a migration to AD.
Furthermore you cannot have any NT4 domain controllers in the domain to upgrade to Exchange 2007.

You need to split this job up first...

Stage 1 - the move to pure AD - no NT4 domain controllers.
Stage 2 - the move from Exchange 5.5 to 2003
Stage 3 - the move from Exchange 2003 to 2007.

If you think you are going to do all of that in a weekend, then you need to think again.

I have just advised a client to do the job over six months, allowing for time for each stage to bed in before moving to the next one.
The move to AD can be quite traumatic for some companies and needs to be carefully planned. There is lots of documentation on the process as people have been doing it for almost seven years now.
Once off NT4, the switch to E2003 from 5.5 is almost pain free in comparison. It isn't 100% pain free, there can be some disruption if not planned correctly.

Finally you need to plan your AD layout quite carefully. If you have remote locations then you need to look at sites and services configuration within AD. This is key with Exchange 2007 as it uses AD Sites and Services to manage email flow.

Simon.

I am not upgrading either machine, I am going to replace them. There will not be a upgrade from 4.0. there is no way to load 4.0 on the new server and do an upgrade from there. can i put win 2003 on the new server and run DC Promo and have it take the place of my NT4 Domain controller. then add the exchange 2007 to the other new server, I am not sure the best way to do the exchange migration, or is it best to recreate the mailboxes and groups(more work)

Whether you are replacing or upgrading, if you want to retain the existing domain then somewhere along the line a NT4 domain controller has to be in place upgraded to Windows 2003. I will often build a special machine to do that so that the machine can be dropped at a later date.

You have said above that you have 8 BDCs at the remote locations. Presuming that those are NT4 machines (because there are no PDCs and BDCs in AD) those all need to be removed before you can even think of installing Exchange 2007.
Furthermore there is no path from Exchange 5.5 to Exchange 2007.

You have to remove both Exchange 5.5 and all NT4 domain controllers so that the domain can be switched to Windows 2000 native before even considering Exchange 2007 deployment.

There are no shortcuts. You are two generations behind, so you have got to catch up before upgrading.

Simon.

so building a interim server, load NT, promote it to pdc, load win 2003 on top is the best way. why do the bdc's have to be reoved before the new exchange 2007 server is brought online?

The BDCs have to be removed because you cannot install Exchange 2007 in to a mixed mode site. You can only install it in to a native mode site which means no NT4 domain controllers.

After you have upgraded the interim machine, you then build your real domain controllers and move the roles over to them. Then you can DCPROMO out the upgraded server and drop it in to a workgroup - net result being that there is no upgraded machines as a DC, just clean builds.

Simon.

The BDC's would just become member servers?

NT4 machines cannot be turned in to member servers. You would have to remove them, wipe them and reinstall them.

Simon.

so I dont need the remote BDC"S for logging local users on to the network? Every one from a remote location will be sent across the wan to the new win 2003 machine to log on to the domain?

You can put domain controllers in the remote locations if you wish. They would need to be Windows 200x global catalog dcs in order to process logins.
The placement of Windows 200x domain controllers and the configuration of sites and services is something that most companies need to deal with. Things are lot more complicated than with an NT4 domain. You will experience the most pain switching to AD than you will migrating off Exchange 5.5.
Simply replacing all NT4 BDCs with an AD DC/GC may not even be the most suitable topology for your network. You need to read the planning white papers on Active Directory or even call in a consultant who can advise you on what is going to be the best thing for you to do.

Simon.

Does exchange 2003 require native mode? I have been looking for an answer on microsofts site with no luck.