If you fail to uninstall AdminPak.msi prior to upgrading Windows Server 2003 to SP1, you cannot uninstall it after the upgrade. When you attempt to uninstall it, you receive:

Windows Server 2003 Administration Tools Pack can only be installed on Windows XP Professional with QFE Q329357 applied, on Windows XP Professional Service Pack 1 or later, or on computers running Windows Server 2003 operating systems.
Setup Failed - Due to an error, Windows Server 2003 Administration Tools Pack Setup Wizard was unable to finish.

To workaround this bug:

1. Download the SP1 version of AdminPak.msi.

2. Right click the AdminPak.msi file from step 1 and press Install.

NOTE: After the installation finishes, both the old and new version of the Windows Server 2003 Administration Tools Pack is installed.

3. Start / Run / Appwiz.cpl / OK.

4. Select the Change or Remove Programs button in the upper left corner of the Wizard.

5. Select Windows Server 2003 Administration Tools Pack and press Remove to uninstall both the Windows Server 2003 version of AdminPak.msi and the Windows Server 2003 with SP1 version of AdminPak.msi.

6. Right click the AdminPak.msi file from step 1 and press Install.