You cannot uninstall an upgraded version of Windows Vista after you use Windows Anytime Upgrade (WAU) to install Windows Vista

After you upgrade Windows Vista by using Microsoft Windows Anytime Upgrade (WAU), you cannot uninstall the upgraded version of Windows Vista.

For example, after you use WAU to upgrade Windows Vista Home Premium to Windows Vista Ultimate, you cannot uninstall Windows Vista Ultimate to revert to Windows Vista Home Premium.

This issue occurs because Windows Vista cannot revert to an earlier version of Windows Vista that does not use WAU. After you use WAU to install Windows Vista, non-WAU installations are not supported.

To resolve this issue, perform a clean installation of the earlier version of Windows Vista. To do this, follow these steps.

Step 1: Back up files

To resolve this issue, follow the steps in the appropriate section.

The computer is connected to the Internet

View the "Back up your files" topic on the following Windows Online Help and Support Web site:

The computer is not connected to the Internet

View the "Back up your files" topic in Windows Help and Support on the computer's hard disk by following these steps:

1. Click Start, and then click Help and Support.
2. In the Search Help box or in the Search online Help box, type Back up your files, and then click Search Help.
3. In the list of topics, click Back up your files.
4. Click the link that best describes the problem that you are experiencing.
5. Follow the suggestions to troubleshoot the problem that you are experiencing.

Step 2: Install Windows by using a clean installation

To resolve this issue, follow the steps in the appropriate section.

The computer is connected to the Internet

View the "To install Windows by using a clean installation" topic on the following Windows Online Help and Support Web site:

The computer is not connected to the Internet

View the "To install Windows by using a clean installation" topic in Windows Help and Support on the computer's hard disk by following these steps:

1. Click Start, and then click Help and Support.
2. In the Search Help box or in the Search online Help box, type clean installation, and then click Search Help.
3. In the list of topics, click To install Windows by using a clean installation.
4. Click the link that best describes the problem that you are experiencing.
5. Follow the suggestions to troubleshoot the problem that you are experiencing.