I've had very little luck capturing with VirtualVCR. I have a Bt-based Hauppauge card, running the universal WDM drivers. It took some doing, but they work in VDUB using the wdm-vfw wrapper, though only in preview, not overlay, mode. Still you can look at and adjust the cropping this way, and I've never had any missing picture issues. DScaler also has an overscan adjustment under the settings -> video adjustments menu, though I'm not sure if this is a global setting (I only know it doesn't affect virtualdub)