Connect network HDD via uPnp or SBM

ok, folks. straight away another n00b question. I use a AVM Fritzbox with an external HDD connected which is set as USB Network Sharing device and as such properly connected as network drive under Win7. I also enabled the MediaServer/streaming functionality and the HDD is shown also as such under Win7 under ‘Network’.

So far so good. Now I am pretty sure that when I first connected the HDD to XBMC I used uPnP and all the contents of the HDD showed, esepcially a folder \DVD with my ripped DVDs. I do not know what happened or what I did then but nowadays when I try to connect the HDD as uPnP device it is found in XBMC when I search for it but then I only see some ‘preconfigured’ folders Pictures, Music and Video (or so) which are not even (physically) on the HDD. There is only my folder \DVD and \Fritz (the latter obviously for the MediaServer capabilities). But the \DVD folder is not shown in XBMC.

The workaround is now that I connected the HDD via SBM as network drive in XBMC. This works and streaming of my ISO files, too. But I wonder whether uPnP would be the more ‘native’ or appropriate way to add streaming video data from my HDD to XBMC? If yes, how comes that once the \DVD folder was shown in XBMC and now suddenly not anymore?

Any ideas? Tried to search here for UpnP but w/o success.