If your hometheatre system has an (in) hdmi port, rather than the (out) port for tv connection, then pop in one of these hdmi to vga and audio converters http://www.amazon.co.uk/gp/product/B00GNVDX7C?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00
and put the jack into your laptop