Yes mate - DVB-C is not supported in MCE/Vista.
Thats why people mostly use Technotrend C-1500 or Floppydtv cards for MCE use, as they psudeo software that tricks MCE into thinking its a DVB-T card. You would also need a hardware cam and card for these to work.
Your card does not have any psudeo MCE software (on the sat version it does) so you would be limited to apps like DVBViewer/MyTheatre etc.
Although there is a vista app called Sceneo VistaTV that intergrates itself into the media center so that could be an option.