I have a situation very much like the one at ImportError: DLL load failed: %1 is not a valid Win32 application, but the answer there isn\'t working for me.
I copied cv2.pyd file from /opencv/build/python/2.7/x86 folder instead of from /x64 folder to C:/Python27/Lib/site-packeges. I followed rest of the instructions provided here.
Added by someone else, not verified: I also copy file cv2.pyd to folder C:/Python27/Lib/site-packages/cv2. It works.