i don't know what you use for capturing but i suggest using vvvv's screenshot node and fraps (i can send a simple patch if you'd like to try). neither of them will degrade performance (i have constant 30 fps) because fraps uses GPU and the HDD, vvvv uses gpu as well if AVS is shot in a compositing window management (so Aero in windows) and a very little cpu. i don't recommend stacking desktop management because then it'll shoot the area of the window if something overlaps it that will be visible as well. you'll need a little standalone utility called window handle picker for this i can send it too.