Choosing to Upgrade or Refresh

A basic decision is whether to upgrade or to perform a new installation. Upgrading refers to leaving the existing Windows NT 4.0 (with Service Pack 5 or later) operating system on your computer and updating it by installing the new Windows Server 2003 operating system. A new installation means completely removing the previous operating system or installing a product in the Windows .NET Server family on a volume that has no previous operating system.

Reasons to Upgrade

Especially for small organizations, doing an upgrade rather than a new installation can make sense. Generally, with an upgrade, configuration is simpler, and your existing users, settings, groups, rights, and permissions are retained. And with an upgrade, you do not need to reinstall files and applications. As with any major changes to the hard disk, however, you should back up the system before beginning an upgrade.

See the following resources for more information:

Regarding upgrading, see the Windows Server 2003 online Help and Support Center section "Operating Systems from Which You Can Upgrade" within the topic "Upgrading Compared with Installing."
If you are upgrading in a domain that includes domain controllers running Windows NT 4.0, see the Help and Support Center topic "Upgrades in a Windows NT 4.0 Domain."
If you want to upgrade and then use the same applications as before, be sure to review applications information in Relnotes.htm (in the \Docs folder on the Setup CD). Also, for the most recent information about compatible applications for products in the Windows Server 2003 family, see the software compatibility section of the Microsoft Web site (http://www.microsoft.com/).

Reasons to Perform a Clean Installation

There are good reasons to perform a clean installation rather than an upgrade ”especially when dealing with large organizations. If you reformat your hard disk and then perform a new installation, the efficiency of your disk might improve (compared with not reformatting it). Reformatting also gives you the opportunity to modify the size or number of disk partitions to make them match your requirements more closely.

If you want to practice careful configuration management ”for example, for a server where high availability is important ”you might want to perform a new installation on a server instead of an upgrade. This is especially true on servers on which the operating system has been upgraded several times in the past.

It's possible to install the Enterprise Edition and also allow the computer to sometimes run another operating system. Setting up the computer this way, however, presents complexities because of file system issues.

More Information

For more information about using multiple operating systems, see the Windows Server 2003 Help and Support Center topic "Deciding Whether a Computer Will Contain More than One Operating System."

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Understanding Server Roles

Computers that function as servers within a domain can have one of two roles: member server or domain controller. A server that is not in a domain is a stand-alone server.

Member Servers

A member server is a computer that

Runs Windows NT 4.0 Server, Windows 2000 Server, or a Windows Server 2003 operating system.
Belongs to a domain.
Is not a domain controller.

A member server does not process account logons , participate in Active Directory replication, or store domain security policy information. Member servers typically function as file servers, application servers, database servers, Web servers, certificate servers, firewalls, and remote access servers.

The following security- related features are common to all member servers:

Member servers adhere to Group Policy settings that are defined for the site, domain, or organizational unit.
Access control exists for resources that are available on a member server.
Member server users have assigned user rights.
Member servers contain a local security account database, the Security Accounts Manager (SAM).

Domain Controllers

A domain controller is a computer that

Runs Windows NT 4.0 Server, Windows 2000 Server, or a Windows Server 2003 operating system.
Stores a read/write copy of the domain database.
Participates in multimaster replication.
Authenticates users.

Domain controllers store directory data and manage communication between users and domains, including user logon processes, authentication, and directory searches. Domain controllers synchronize directory data using multimaster replication, ensuring consistency of information over time.

Active Directory supports multimaster replication of directory data between all domain controllers in a domain; however, multimaster replication is not appropriate for some directory data replication. In this case, a domain controller, called the operations master, will process data. In an Active Directory forest, there are at least five different operations master roles that are assigned to one or more domain controllers.

As the needs of your computing environment change, you might want to change the role of a server. Using the Active Directory Installation Wizard, you can promote a member server to a domain controller, or you can demote a domain controller to a member server.

Stand-Alone Servers

A stand-alone server is a computer that

Runs Windows NT 4.0 Server, Windows 2000 Server, or a Windows Server 2003 operating system.
Is not a member of domain.

If a server is installed as a member of a workgroup, that server is a stand-alone server. Stand-alone servers can share resources with other computers on the network, but they do not receive any of the benefits provided by Active Directory.

For more information, see the Windows Server 2003 Help and Support Center.

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