I noticed that the Windows.Xbox.Speech.Recognition idl looked a bit odd and it used stuff from midl2 so I removed the idl and cpp files and pretty much started from scratch. It took me a while to create the idl and get guid and stuff, but setting up the cpp files and tidying it up into 5 files from 30 small file took a lot longer since I had to manually tidy the funcs and add a debugging line to each of them.