Play the video in the preview monitor, stop it at the exact frame you want. Under File, click Export Frame. This frame will be saved as a bitmap, and should appear in the project box, (top left of screen in PP 1.5). Right click and click Insert. This should put it in the timeline. Right click it, and one of the options that appears will be to adjust the length of it. Or, you can use the mouse to drag the end of it until it's exactly 25 frames (assuming 25 fps).

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