I can't remember where but most of my SMB shares suddenly worked when i was researching how to get them to work in XBMC. They gave some specific directions on how to set it up on the PC end of things to work with XBMC and then I did the same again in emulators.
My Xbox only has the original hard drive, so there's maybe 3gb or so of space left on it. My Genesis romset is something like 680mb and apparently my SCD set is about 55gb for some reason. I tried looking for guides but all the ones I found only deal with PC to PC running XBMC/Kodi
try this one?