If you are deploying a new Exchange organization, and you are preparing your Active Directory schema and domain by using a computer running Windows Server 2008, you must first install the Active Directory Domain Services remote management tools on Windows Server 2008.
To install ADDS remote management tools run command:

ServerManagerCmd -i RSAT-ADDS

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Next you must install Windows PowerShell.

To install Windows PowerShell run command:

ServerManagerCmd -i PowerShell

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? Preparing Active Directory and Domains for Exchange 2007

setup /PrepareSchema

setup /PrepareAD /OrganizationName:contoso

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To install the Windows Server 2008 operating system prerequisites for a computer that will host the Hub Transport, Client Access, and Mailbox server roles.

You must run all this commands:

ServerManagerCmd -i Web-Server

ServerManagerCmd -i Web-ISAPI-Ext

ServerManagerCmd -i Web-Metabase

ServerManagerCmd -i Web-Lgcy-Mgmt-Console

ServerManagerCmd -i Web-Basic-Auth

ServerManagerCmd -i Web-Digest-Auth

ServerManagerCmd -i Web-Windows-Auth

ServerManagerCmd -i Web-Dyn-Compression

ServerManagerCmd -i RPC-over-HTTP-proxy

Installation Exchange 2007 SP1 on Windows Server 2008

Remember if you deploying Exchange on Windows Server 2008, you must use Exchange Server with Service Pack 1.

Step 1. Run setup.exe file.

Step 2. On the Introduction page click Next.

Step 3. On the License Agreement page read the license agreement, select I ACCEPT the terms in License Agreement, and then click Next.

Step 4. On the Error Reporting page select YES, and then click Next.

Step 5. On the Installation Type page select Typical Exchange Server Installation, and then click Next.

Step 6. If you have any client computers running Outlook 2003 or earlier select YES, and then click Next.

Step 7. On the Readiness Checks page click Install.

Step 8. On the Completion page click Finish.