Considerations for computers that contain more than one operating system

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.

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: