Hardware Requirements for Installing Microsoft Exchange 2007:

Below are the hardware requirements to install MS Exchange 2007 on any system. The below mentioned minimum requirements should be met to install the software:

Processor	x64 architecture-based computer with Intel processor that supports Intel 64 architecture (formerly known as Intel EM64T) AMD processor that supports the AMD64 platform Intel Itanium IA64 processors not supported Intel Pentium or compatible 800-megahertz (MHz) or faster 32-bit processor (for testing and training purposes only; not supported in production)	It is supported to install the Exchange management tools on a computer that has a 32-bit processor. Note: It is not supported to install Exchange 2007 server roles on a computer that has a 32-bit processor in a production environment. You can install Exchange 2007 server roles on a computer that has a 32-bit processor in testing and training environments only.
Memory	Minimum: 2 gigabytes (GB) of RAM Recommended: 2 GB of RAM per server plus 5 megabytes (MB) of RAM per mailbox
Paging file size	Use the following calculations to determine the value to type in the Initial Size (MB) box in the Virtual Memory dialog box: If the server has 8 gigabytes (GB) of RAM or less: A minimum page file size that is the amount of RAM plus 10 MB. A recommended page file size that is the amount of RAM multiplied by 1.5. If the server has more than 8 GB of RAM: The amount of RAM plus 10 MB. If you experience virtual memory issues, set the page file to the amount of RAM multiplied by 1.5.	.
Disk space	At least 1.2 GB on the drive on which you install Exchange An additional 500 MB of available disk space for each Unified Messaging (UM) language pack that you plan to install 200 MB of available disk space on the system drive In Exchange 2007 RTM, a hard disk drive that stores the message queue database on an Edge Transport server or Hub Transport server with at least 4 GB of free space In Exchange 2007 SP1, a hard disk drive that stores the message queue database on an Edge Transport server or Hub Transport server with at least 500 MB of free space	.
File format	Disk partitions formatted as NTFS file systems.

Checklist on Domain controllers before proceeding with Exchange 2007 Installation:

Domain controllers running on Windows 2003 OS:

• For the release to manufacturing (RTM) version of Exchange 2007 and for Exchange 2007 Service Pack 1 (SP1), in each domain (including child domains) where you have the Exchange Enterprise Servers and Exchange Domain Servers groups and therefore must run Setup /PrepareLegacyExchangePermissions, you must have at least one domain controller that is running Windows Server 2003 SP1 or a later version.
• For Exchange 2007 RTM and Exchange 2007 SP1, in each domain (including child domains) where you plan to install Exchange 2007, you must have at least one domain controller that is running at least Windows Server 2003 SP1.
• In each Active Directory site where you plan to install Exchange 2007, you must have at least one domain controller that is also a global catalog server and is running Windows Server 2003 SP1 or a later version.
• If you have any domain controllers that are running Windows 2000 Server, when you prepare Active Directory and domains for Exchange 2007 RTM and when you install Exchange 2007 RTM, you must run Setup.com from a Command Prompt window, and you must use the /DomainController parameter to specify a domain controller that is running Windows Server 2003 SP1or a later version. When you prepare Active Directory and domains for Exchange 2007 SP1 and when you install Exchange 2007 SP1, you do not have to specify a domain controller that is running Windows Server 2003 SP1 or a later version.
• Although you cannot install Exchange 2007 RTM on a server running Windows Server 2008, Exchange 2007 RTM is supported for use with Windows Server 2008 directory servers. Similarly, Exchange Server 2003 Service Pack 2 (SP2) cannot be installed on computers running Windows Server 2008, but it is supported for use with Windows Server 2008 directory servers.
• Exchange 2000 Server Service Pack 3 (SP3) cannot be installed on computers running Windows Server 2008, nor is it supported for use with Windows Server 2008 directory servers. An Exchange 2000 SP3 server can exist in an Active Directory forest that contains Windows Server 2008 directory servers, but Windows Server 2008 directory servers should not be installed in Active Directory sites that contain Exchange 2000 servers.

Domain controllers Running on Windows 2008 OS:

Exchange 2007 SP1, Exchange 2007, and Exchange 2003 SP2 are supported in environments that either partly or entirely use writeable Windows Server 2008 directory servers.

Exchange 2000 Server Service Pack 3 (SP3) and all previous versions of Microsoft Exchange are not supported for use with Windows Server 2008 directory servers. The following restrictions apply with respect to Exchange 2000 SP3:

• Exchange 2000 SP3 can exist in an Active Directory forest that contains Windows Server 2008 directory servers, but Windows Server 2008 directory servers should not be installed in Active Directory sites that contain Exchange 2000.
• If Windows Server 2008 directory servers must be deployed in Active Directory sites that contain Exchange 2000, you must first hard code Directory Service Access (DSAccess) on the Exchange 2000 servers in the site to point to directory servers running Windows Server 2003 or Windows 2000 Server.

·  No version of Microsoft Exchange uses read-only domain controllers or read-only global catalog servers. However, Microsoft Exchange works in environments that include read-only domain controllers or read-only global catalog servers, as long as there are writeable domain controllers available. Exchange 2007 effectively ignores read-only domain controllers and read-only global catalog servers. Exchange 2003 also ignores read-only domain controllers and read-only global catalog servers in default conditions where Exchange components automatically detect available domain controllers. No changes were made to Exchange 2003 to make it read-only directory server-aware. Therefore, trying to force Exchange 2003 services and management tools to use read-only global catalog servers may result in unpredictable behavior.