Wow, I didn't know they made capture cards with HDMI.
Unfortunately, I think there is nothing that will be able to replace/adapt that PCI-e connector you need. However, if what you intend to do is edit and/or encode HD movies, you might also want to consider upgrading your PC. Reasonably prices machines (~500-600$) can probably perform 3-6 times better than what you currently have AND will have the required PCI-e connector.
Here's the thing - I am not looking to do anything with the card, except play back video. My main computer is a self-built Vista 64-bit machine, with an E8400 3.0 GHZ, Asus P5Q Pro MB, 650 PSU, and 8 GB RAM. This computer of course has a PCI-e slot, but when I compose, and have alot of virtual instruments playing back simul, my CPU usage is WAY up there, and do not want to add any CPU usage with that card. So, I want to use a different computer with that card, and as I have a older Dell laying around, I would much rather use that one, than spend money to build another computer - just for a PCI-e slot. This is why I was hoping for an adapter. But it's looking more and more like another computer is what i am going to have to do.