Warning: Windows disk letters differ

Windows was installed on the source computer and the destination computer on two different disk drive letters or paths. For example, the source computer installed Windows on D:\WINDOWS but the destination computer installed Windows on C:\WINDOWS.

This error can also happen if you upgraded Windows Server 2000, which uses C:\WINNT, to Windows Server 2003.

How to Fix This Error

To fix this error, re-install Windows on the destination computer using the same disk drive letter and path as the source computer.

How to Re-arrange Disk Letters

By default disk letters are assigned alphabetically starting with C:, D:, E:, etc. (Letters A: and B: are reserved for removable diskette drives.)

You may need to create dummy disk partitions on the destination computer so that the assigned disk letters “line up” with the assigned disk letters on the source computer.

Click on Start -> Control Panel -> Administrative Tools -> Computer Management. Then click on Storage -> Disk Management.

If necessary, create one or more dummy disk partitions. For example, to install Windows on drive letter D: create a small dummy primary partition #1 and then create a large extended partition with a logical partition #2. Partition #1 will be assigned C: (small), while partition #2 will be assigned D: (large), so you can install Windows on partition #2. (This example assumes that your computer has exactly one disk. If not, see below.)

Assigning Disk Drive Letters with Multiple Disks

If your computer has two or more physical disks, the default drive letter assignment is slightly different. By default the first partition on each physical disk is assigned a drive letter starting with C:. Then subsequent partitions are assigned the remaining drive letters.

For example, if your computer has two disks and four partitions on each disk (total eight partitions), Windows will assign the disk letters as follows: The first disk gets C:, E:, F:, G:. The second disk gets D:, H:, I:, J:.

Using \WINNT instead of \WINDOWS

If the source computer was upgraded in-place from Windows NT (or Windows 2000) to Windows 2003 the installation folder might be named \WINNT instead of \WINDOWS. When installing Windows Server 2003 on a fresh computer (e.g., on the destination computer) Microsoft Setup does not give you the choice to change the folder name to \WINNT.

To force the installation of Windows 2003 to \WINNT you will need to use an unattended answer file, A:\WINNT.SIF. In the section [Unattended] set TargetPath=\WINNT (see the link for instructions). Insert the diskette containing A:\WINNT.SIF just before you boot the initial text-mode for Microsoft Setup.

Alternate method: Do a minimal installation of Windows 2000 Server. Then upgrade it in-place to Windows 2003.

Creating the Answer File A:\WINNT.SIF

For instructions on creating the answer file A:\WINNT.SIF see http://www.networkclue.com/os/Windows/install/unattended-install.aspx.

For your convenience an example of the content of A:\WINNT.SIF is shown below. Use NOTEPAD.EXE and copy/paste the following text:

;SetupMgrTag
[Data]
    AutoPartition=1
    MsDosInitiated="0"
    UnattendedInstall="Yes"

[Unattended]
    UnattendMode=FullUnattended
    OemSkipEula=Yes
    OemPreinstall=No
    TargetPath=WINNT

[GuiUnattended]
    AdminPassword=password
    OEMSkipRegional=1
    TimeZone=4
    OemSkipWelcome=1

[UserData]
    FullName="My Full Name"
    OrgName="My Company Name"
    ComputerName="TempName"
    ProductID="XXXXX-XXXXX-XXXXX-XXXXX-XXXXX"

[Networking]
    InstallDefaultComponents=Yes

Note especially the line TargePath=WINNT. The line instructs Setup to install Windows to \WINNT instead of to \Windows.

Insert the diskette containing A:\WINNT.SIF and boot the Windows 2003 install CD. Very early during the text-mode (blue screen) setup process the diskette light will briefly illuminate and then go out. When the computer leaves text-mode you can remove diskette.

Installation will proceed on \WINNT.

Overriding the Warning Message

In general you should not override this warning message. Although UMove knows how to move Active Directory to an alternate drive letter, many applications cannot be moved this way.

The following applications cannot be moved to an alternate drive letter:

• Certificate Services
• DHCP Service
• Exchange Server
• Internet Information Services (IIS)
• SharePoint Services
• Terminal Services
• WINS Service

These applications embed the disk letter into binary data files that cannot be changed. The only workaround is to re-install them and manually export/import the associated data.

How to override this warning