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500.19 %1 is not a valid Win32 application

While troubleshooting a “500 Internal Server Error”, I saw this error in the Failed Request Tracing log:

500.19 Internal server error 
%1 is not a valid Win32 application
0x800700c1
500.19 %1 is not a valid Win32 application

Solution for “500.19 %1 is not a valid Win32 application” error

After comparing the working and non-working servers, I saw that enable32BitAppOnWin64 was set to True in the non-working server. The working server had this value to False.

We set it to False in the non-working server. The 500 error disappeared.

For more information, please check the official Microsoft documentation.

Ned Sahin

Blogger for 20 years. Former Microsoft Engineer. Author of six books. I love creating helpful content and sharing with the world. Reach me out for any questions or feedback.
Categories IIS

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