[Groucho2004]

Originally Posted by TheFluff

Avs+ passes LOAD_WITH_ALTERED_SEARCH_PATH to LoadLibraryEx, which means the dependency search will start in the folder the loaded module is in (that is, the plugins folder). Putting libfftw3.dll in the plugins dir is thus fine.

The calls to the fftw DLLs are in the plugins themselves, for example in dtftest it's this line:
hLib = LoadLibrary("libfftw3f-3.dll");

Anyway, I tested this and AVS+ does not change what I stated above.