Alert on June 13, 2017
New App Pool unexpectedly defaults itself to Win32
When you use IIS Manager to make a new Application Pool , it defaults to win32 not win64 on Windows 10 Pro. This, of course, leads to IIS Server Error 500 with Error Code 0x800700c1, if you are in fact loading custom win64 ISAPI extensions.
Solution: go into Advanced Settings for the App Pool and toggle True to False for enabling 32-bit.
This seems to me to be a new/opposite behavior in IIS Manager. I am not sure when it started but it must have been fairly recently.
This is the detail that I picked up today:
Detailed Error Information:
Module IsapiModule
Notification ExecuteRequestHandler
Handler ISAPI-dll
Error Code 0x800700cl
Requested URL http://localhost:80/scripts/runisa64.dll?r:version
Physical Path D:\Apps\HREFTools\WebHub\bin\whRunner\runisa64.dll
Logon Method Anonymous
Logon User Anonymous