Installing Blackberry Enterprise Server Express

Just about to head home, so a quick pointer...
You need to install the exchange server management tools on the BESX box to get the MAPI and CDO installed so it can talk to exchange.
The account you use to install the software needs to be a local admin to the machine, but not a domain admin.

Huge page of resources here for planning and installing BESX http://docs.blackberry.com/en/admin/deliverables/14347/BES_overview_Xprs_991919_11.jsp

With Exchange 2007, you do not want to install the Exchange management console on the BES server, as this no longer installs the MAPI and CDO components that you need for BES.  What you need to do is download and install the MAPI and CDO components alone:
http://www.microsoft.com/downloads/details.aspx?familyid=E17E7F31-079A-43A9-BFF2-0A110307611E&displaylang=en 

The planned install of BESX is on a 2003 DC running Office 2007. Exchange is not installed on it.

The 2008 server is running Exchange 2007. If I understant the first two replies, that appear to conteract each other.

In Active Diretory Users and Computers on the 2008 server, I think I should create the Besadmin user with admin rights. is that correct?

It doesn't matter which OS your BES is using, you have to install the MAPI and CDO components required for Exchange 2007, as I described above, since that is the version of Exchange that you're using.
The BES Admin account needs to be in the local Administrators group on the BES server (Windows 2003 server), not in the Domain Admins group. So, you need to create the BES Admin user in AD Users and Computers on the Windows 2008 domain controller. Then, you need to open the Administrative Tools/Computer Management/Local Users and Groups on the Windows 2003 server and make the domain BES Admin account a member of the local Administrators group.
Here's an article about setting this up that is very helpful if you don't have this already:
http://tinyurl.com/35j93vm
Download this guide and it will have all the info you need for a successful installation in your environment.

I logged into the 2003 as the administrator of the domain, went into administrator tools, computer management but I don't see Users and Groups in the structure on the left sde. I logged onto the 2008 and cheked it out. Users and Groups don't show up there either. Is there an option anywhere to display it? I've never seen this happen before.

I tried adding besadmin into the built-on administrators security group, but it would not allow me to save it. I also tried adding the domain administrator.

We have a 2000 member server in the network. Will it work there and connect to Exchange 2007?

There is no reason you wouldn't be able to add this user to the Administrators group unless you don't have sufficient permissions in Active Directory. You would need to be logged on to with domain admin credentials.

I setup a member server ans your suggestions worked fine.