Splitting 1 domain into 2 and upgrading to W2K3

[ClowneUser]

Hi all,
Hopefully someone out there can help me to make sense of what I'm being asked to do. Here is the scenario:
Company A used to have 2 sites, Site A and Site B at 2 different locations in the UK.
Now Site B has split from Company A and has become Company B, still at the same geographical site.
Company A and Company B are linked by a WAN as Company B still shares a manufacturing ERP system with Company A. (The companies are still under the same ownership).
However, Company B has its own Exchange server, file servers, etc.
The AD is Windows 2000 and both companies are still in one domain companyA.co.uk.
We have been asked to upgrade our domain to 2003 from 2000 and to give CompanyB their own domain.
I know that Forest topology has come into play in 2003 and wondered if anyone could tell me what to consider when creating a forest? In the scenario above is there a need for 2 forests, 2 domains, or would 1 forest with 2 domains do the trick?
As the 2 companies are moving in different directions, Company B may decide at some point in the future that they do not need to use the ERP system hosted by Company A and there would then be no need for the WAN connection, so my thought is, to save any future headaches a 2 forest approach would be best.
Any advice would be appreciated, including any problems we may encounter by doing this.
Thanks in advance..

 

[Davetoo]

I would create two disparate domains with a trust. That way when the companies part ways, you simply break the trust.

I'm Certifiable, not cert-ified.
It just means my answers are from experience, not a book.

There are no more PDC's! There are DC's with FSMO roles!

 

[ClowneUser]

Thanks for that.
I think I'd talked myself into the 2 domain scenario, but it's the Forest I'm confused about.
Would I need to create 2 forests with a domain in each, so that in the future it will be easier to just cut the link and break the trusts?
If I have 2 domains in 1 forest and the physical link between the 2 companies is broken, can I then just remove the domain for CompanyB from the forest?

Or do i need a forest at all? Is it compulsory in W2K3 to have a forest or can I ignore it and just go with the 2 domains as suggested?

 

[Davetoo]

I'd create separate domains entirely. If you're only going to have the one domain in each, then you don't have to worry about the forest issue.

http://technet.microsoft.com/en-us/library/cc740018.aspx

will help.

I'm Certifiable, not cert-ified.
It just means my answers are from experience, not a book.

There are no more PDC's! There are DC's with FSMO roles!