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Considerations for computers that contain more than one operating system

Updated: January 21, 2005

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Considerations for computers that contain more than one operating system

On a computer with an appropriate disk configuration (outlined in the table later in this topic), you can install more than one operating system, and then choose between the operating systems each time you restart the computer.

Note

  • On an Itanium architecture-based computer, you can install Windows XP 64-bit Edition (Itanium) and the Itanium-based versions of Windows Server 2003. In this topic and other topics about installing multiple operating systems, information about operating systems that you cannot install does not apply. For example, information about Windows 2000 or Windows NT 4.0 does not apply to an Itanium architecture-based computer.

For example, on an x86-based or x64-based computer, you could set up a server to run Windows Server 2003, Enterprise Edition, most of the time, but allow it to sometimes run Windows NT Server 4.0 Enterprise Edition in order to support an older application. (However, to do this you would need to make specific file system choices and would need Service Pack 5 or later, as described in Multiple operating systems and file system compatibility.) During restarts, a display would appear for a specified number of seconds, allowing you to select between the two operating systems. (You can specify a default operating system that will run if no selection is made during the restart process.)

The following table shows the disk configurations on which you can install more than one operating system.

Important

  • You must follow the requirements in the following table. For example, on a basic disk, you must install each operating system in a separate partition. This ensures that each operating system does not overwrite crucial files that are needed by another operating system.

 

Disk configuration Requirements for multiple operating systems

Basic disk or disks

You can install multiple operating systems, including Windows NT 4.0 and earlier operating systems, on a basic disk. Each operating system must be on a separate partition or logical drive on the disk. A partition or logical drive is a section of the disk that functions as a separate unit. Different partitions often have different drive letters; for example, C: and D:.

Single dynamic disk

You can install only one operating system.

However, if you used Windows 2000 or Windows XP to change a disk with no partitions directly to a dynamic disk, you must revert the disk to basic before you can install an operating system on it. For more information, see the Note after this table.

Multiple dynamic disks

Each dynamic disk can contain one installation of Windows 2000, Windows XP, or a product in the Windows Server 2003 family. No other operating systems can start from a dynamic disk.

However, if you used Windows 2000 or Windows XP to change a disk with no partitions directly to a dynamic disk, you must revert the disk to basic before you can install an operating system on it. For more information, see the Note after this table.

Master boot record (MBR) disk on an Itanium architecture-based computer

You cannot start operating systems from an MBR disk on an Itanium architecture-based computer. You must use a GPT disk for this purpose.

GUID partition table (GPT) disk on an Itanium architecture-based computer

You can install one or more operating systems on a GPT disk on an Itanium architecture-based computer. The guidelines in this table for basic and dynamic disks apply to GPT disks on Itanium architecture-based computers.

On an Itanium architecture-based computer, the operating systems that you can install include Windows XP 64-bit Edition (Itanium) and the Itanium-based versions of Windows Server 2003. On an Itanium architecture-based computer, you cannot install earlier operating systems, such as Windows 2000.

Note

  • If you used Windows 2000 or Windows XP to change a disk with no partitions directly to a dynamic disk, you must revert the disk to basic before you can install an operating system on it. All data will be lost in this process, so back it up first. You can then use Windows 2000 or Windows XP to revert the disk, or you can use Windows Server 2003 Setup. To use Windows 2000 or Windows XP, follow the instructions in Help for your operating system. To use Windows Server 2003 Setup, during the partitioning phase, find the dynamic disk among the list of available partitions and then delete it (which erases all data on all volumes). You will be prompted to confirm your action. After you do this, the disk will contain only unpartitioned space, and you can use Setup to create a new (basic disk) partition on it.

Reasons to install only one operating system

Setting up a computer so that you can choose between two or more operating systems at startup does have an advantage: it allows you to use applications that run only with a particular operating system. However, there are definite reasons to install only one operating system:

  • Each operating system uses valuable disk space.

  • Compatibility issues, especially file system compatibility, can be complex. For more information, see Multiple operating systems and file system compatibility.

  • On a dynamic disk (a storage type available with products in the Windows Server 2003 family), you can have only one operating system per disk. Dynamic disks also will not work with some operating systems. For more information, see the table earlier in this topic.

  • It is no longer necessary to maintain multiple operating systems as a safeguard against problems with starting the computer. With products in the Windows Server 2003 family, you have other options for system recovery. For example, if you have a problem with a newly installed device driver, you can use Safe Mode, in which Windows Server 2003 restarts with default settings and the minimum number of drivers. For more information about Safe Mode and other options, see Understanding Disaster Recovery.

Specific details to consider

Before you decide to set up a computer with more than one operating system, review the topics that apply to your situation:

 

Operating system that can alternate with Windows Server 2003 Topics to review

Another product in the Windows Server 2003 family

Windows 2000

Windows NT 4.0

Windows 98 or Windows Millennium Edition

MS-DOS

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