I am using one video card, an older one as well (NVIDIA GeForce GT 630). The two 24" monitors are both plugged into the same card (both via DisplayPort). They have independent displays -- it's set to Extend but of course it's not as if the system doesn't know how to select "full Screen" on either monitor (just about all programs know how to distinguish the separate monitors).
Smooth functioning: Camtasia provides a lot of nice features in a fluid interface that makes creating screen capture videos and processing them a breeze. You can set the program to record either the screen or a PowerPoint presentation. You can also choose to record your entire screen or only a portion of it that you preset before recording begins. The recordings, themselves, are clear and crisp, providing you with an excellent framework on which to put all the finishing touches and effects you want.