A few comments at random:
I’ve not found many good solid capture cards, but yes I do believe the assertion is correct, that they do not capture from the computer (unless you use s-video out of your video card and pipe it right back into the video capture) – they’re more for external sources, like TV.
I don’t know how it works, but I would consider it possible that the (I’ve not seen one recently) ATI all-in-wonder, since it captured input AND was a video card, might possibly do its work without crushing the CPU. Just you’d be crushing your GPU, which still impairs its ability to capture PC gaming, since it’ll crush the game’s performance.
One possibility for credit carding for online purchases without a real credit card is to look into the prepaid gift card market. I know at least VISA does this, and their prepaid cards will do just fine and dandy online. However, there may be cost overhead, and the card company might insist you divulge personal information to accompany the gift card, since the original activation of the card was not tied to you, for purposes mostly developed in response to credit card fraud for real credit cards. I don’t like them, but in a pinch it might just do the trick, if you’re really wanting to purchase things online.