"WINNT32.EXE is not a valid Win32 application" error message when you try to run the Winnt32.exe program from the installation CD for x64-based versions of Windows Server 2003 and Windows XP Professional x64 Edition
Assume the following scenario: You try to install an x64-based version of Microsoft Windows Server 2003 or Microsoft Windows XP Professional x64 Edition on a computer that is already running a 32-bit version of Windows. You do this by running the Winnt32.exe program from the x64-based installation CD. In this scenario, you receive the following error message:
<CD_drive>:\AMD64\WINNT32.EXE is not a valid Win32 application.
To resolve this problem, start your computer from the installation CD for the x64-based version of Windows Server 2003 or for Windows XP Professional x64 Edition. When you do this, the Setup program automatically starts.
For more information about dual-boot configurations, click the following article number to view the article in the Microsoft Knowledge Base:
896455 Programs become unstable or do not start after you install an x64-based version of Windows on the same partition as a 32-bit version of Windows
For more information about how to set up x64-based versions of Windows, click the following article number to view the article in the Microsoft Knowledge Base:
896334 Setup and installation considerations for Windows x64 Edition-based computers
Technical support for Windows x64 editions
Your hardware manufacturer provides technical support and assistance for Microsoft Windows x64 editions. Your hardware manufacturer provides support because a Windows x64 edition was included with your hardware. Your hardware manufacturer might have customized the Windows x64 edition installation with unique components. Unique components might include specific device drivers or might include optional settings to maximize the performance of the hardware. Microsoft will provide reasonable-effort assistance if you need technical help with your Windows x64 edition. However, you might have to contact your manufacturer directly. Your manufacturer is best qualified to support the software that your manufacturer installed on the hardware.
For product information about Microsoft Windows XP Professional x64 Edition, visit the following Microsoft Web site:
Microsoft Windows Server 2003, Standard x64 Edition, Microsoft Windows Server 2003, Enterprise x64 Edition, Microsoft Windows Server 2003, Datacenter x64 Edition, Microsoft Windows XP Professional x64 Edition