I have this same problem, and mine is caused by the design of the integrated audio circuitry on my motherboard - it can't record directly from line-out.
Try playing some music on your computer (anything with any program, just something to get sound out of your speakers). Find the sound recorder in the accessories submenu under the Start menu, and press record. If you don't hear anything while playing it back, then you probably have the same problem as me. You might try looking at some settings in the control panel just to be sure; FRAPS help will tell you where to go.
Better to be nouveau than never to have been riche at all.