Are there adapters for MiniDisplay port screens to HDMI video cards I am wondering if I can connect an Apple Cinema Display with a MiniDisplay port to an HDMI video card.
The short answer is yes.

It's not a common conversion (normally it's a DisplayPort to HDMI), but it can be done.  To do so, you need an active adapter to go from HDMI to DispayPort because the signaling is completely different and needs to be recreated so it will work.