Why 0x8007000B on one Windows 10 Home PC and not on Another

I have a program that is meant for mix platforms. I have tested the same install able on Win 7 Pro 64 bit Win 10 Pro 64 bit Win 8.1 Pro 64 bit Win 10 upgraded from the above 8.1

Dozens of users have various flavors of Win 7.

But: I have one user that gets "An attempt was made to load a program with an incorrect format. (Exception from HRESULT: 0x8007000B)" at the point where a particular DLL loads... actually that DLL loads and has an issue when a particular dependent DLL loads.

Given that I can point at a dozen 64 bit machines that work, I suspect some property of the Windows 10 Home Edition (that upgraded from a Win 7 home) PC. I have a log file that demonstrates the same program ran OK before the Windows 10 upgrade.

What configuration settings on the user's PC should I be looking for?

One possibility is trying to load 32-bit DLL from a 64-bit executable (this can happen when LoadLibrary is used explicitly with e.g. a full path).

Another reason could be a damaged DLL (which might be actually the more likely case here because of the Windows upgrade). If the DLL is in Windows\system32, there is a good chance that if the particular DLL is renamed (e.g. to *.bad), the Windows protection system might recover the DLL to the proper version and resolve the issue.