Server surgery

Wondering if you could give me a few pointers.

At present the company have 2 domains.
The old one (A) is linked to a company abroad and is not the 'main' DC in the forest, it holds AD DNS Exchange etc etc.
The new system (B) Has a Fantastic spec but basically sits on its arse handing out a few files now n then.
From what a colleague has told me we cannot create a 2way trust between them without linking B to abroad. Not gonna happen.

Basically i want to establish a new Domain, completely independent of any other company/system.

My first thoughts were to transfer files from B to A and create appropriate shares, login scripts and the like and switch everyones machines from domain B to A, allowing everyone to carry on as normal (Would it be possible to keep everyones desktop profiles/settings the same even tho they would be switching domains??)

This would free up B, which i would like to wipe and do a fresh install of Server2008 R2 (call this C), creating a new AD, Exchange, file/print services etc etc,
Once setup, tested and running, transfer the data to C, create shares and the like and switch everyone to the new domain, with new user accounts and passwords.
Eventually deleting A.

a) Why does the dc in someone else's (parent company?) forest still exist?
Or, to put it another way, if you wipe the dc in someone else's forest will there be any negative business or CLM repercussions?

b) Exchange running on the same OS install as a domain controller and (with the exception of SBS) is not a good idea. Seriously, don't do this. If you're small enough (and from the hardware, it sounds like you are) virtualise the exchange role/all server roles on the newer hardware.

While running exchange on the DC is not recommended, in many (most?) primary schools that is what is done and it runs fine.

Primary schools rarely have the luxury of more than one server to play with.

What's the OS on Server B? - Could you boot up a virtual Server? - it would have to be part of the forest.

Elsiegee40 - Your quite right, but when replacing if you can get them to spend that little bit more on a server you can run some Guest Virtual Machines, making life a whole lot easier!

Hence the recommendation to virtualise the roles - you still get everything on one server, but you don't create a situation you'll regret later on.

Server B has 2007 R2
A has 2003

Cant risk messing anything up with the parent group (abroad) but it is the intention to break the links (just the ones connecting our servers...)
So how come Exchange inst recommended on a DC? (I remember my primary school days, 5 inch floppies, seems a joke now...)

Thanks for the responses guys.

It may be a typo, but it should read 'Do not install on a DC!' and has been this was since Exchange 2000. As the others have said, virtualise it as soon as you can!

While elsiegee40 is correct that many primary schools do install Exchange on a DC, there are a few issues (off top of my head, probably more):

You can be backing yourself into a corner, upgrade-wise. If you install exchange on a DC, you can't demote that DC and expect Exchange to work. This introduces faffing when moving to a newer version of Exchange or upgrading your domain.

It adds complexity for DR / troubleshooting situations, I'd much rather be fixing Exchange (or a DC) than trying to fix Exchange and a DC on the same install. Having them separate means it's a lot easier to troubleshoot issues.

Exchange provides publicly accessible services. It needs a global catalogue to function (not just a DC). Especially if you're using OWA you just made your GC publicly contactable.

(on 2003 at least) you'll have long shutdown times when exchange tries to talk to a DC, but can't because the DC is shutting down.

I'm saying this as someone who inherited a network with an LEA-configured NT4 PDC that had Exchange 5.5, Symantec Web Security (web proxy) and was also used to host curriculum app shares. For ~1000 users. They kept that quiet at the interview.

I get flashbacks.