su msdn ho trovato questo ...filo di speranza

32-bit DLLs on a 64-bit OS Logan1337 | Edit | Show History
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This exception can occur when a .NET application running on a 64-bit platform attempts to load a DLL that does not support native 64-bit execution. If the application is built in platform-agnostic (i.e. "Any CPU") mode, it will launch in 64-bit mode on the host operating system, leading to this problem. To fix this, you can force the application to run in 32-bit mode by compiling for x86 architecture explicitly, forcing the program to launch in WoW64 mode on the 64-bit system, and allowing the 32-bit DLL to be accessed.

ma non ho capito bene cosa dovrei fare per forzare l'esecuzione da 64 a 32