When you try to install Windows Vista, you cannot select the Upgrade option in the Install Windows dialog box. Additionally, you receive the following error message in the Install Windows dialog box:
Upgrade has been disabled - To upgrade, start the installation from Windows
This issue may occur if you run Setup by using the Windows Vista installation media.
To resolve this issue, use one of the following methods.
If you are trying to install Windows Vista on a computer that currently has no installed operating system, click Custom (advanced) on the Which type of installation do you want? screen. Then, perform a clean installation of Windows Vista.
If you are trying to upgrade your current installation of Windows to a 32-bit version of Windows Vista, exit Setup, restart the computer by using the currently installed version of Windows, and then restart the Windows Vista installation process. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
932616 Installation choices for consumer versions of Windows Vista (32-bit only)
If you are trying to upgrade your current installation of Windows to a 64-bit version of Windows Vista, you must perform a clean installation of Windows Vista.
Note Make sure that you back up all data on the computer before you run the installation process. Then, restore the data to the newly installed Windows Vista system.
For more information about how to install Windows Vista, click the following article numbers to view the articles in the Microsoft Knowledge Base:
932795 Installation choices for 64-bit consumer versions of Windows Vista