sharing files on NAS to xb0x360 with vista home premium

Can anyone help me.
Late last year i was lucky enough to get an evaluation copy of Vista
Ultimate and was very impressed. Especially as it enabled myself to use my
media files stored on my NAS through media centre to my XBOX360 and to my
Philips Streamium. This was effortless under the evaluation version and was
my reason for Purchasing a copy of Home Premium.
I am now disappointed to find that although media centre within the PC that
has vista newly installed can see and use the NAS media files, it will not
send the folders to the other devices. The only thing it seems to want to
share is what is under the standard my music and my pictures and my videos
folders etc.
I have configured media sharing in wmp11 and added removed and added again
the monitored network folders to no avail.

At the moment i feel somewhat cheated or is this a limitation of home
premium as opposed to Ultimate?
--
Regards

Brian