If I had to do this, I would use a capture device of some sort (either an internal capture card or a usb based device) and make a copy of the video on the hard drive of my computer. Here is an example of a usb device designed for this purpose: http://www.newegg.com/Product/Product.aspx?Item=N82E16815116048
Usually, the device will come with software that will allow you to make still image captures from the video.
Or you can use a video player like VLC to get a single image from wherever you want in the video. Pause the video once you have it where you want, then click Video–>Snapshot.
Quality of VHS video is not great to begin with, and snapshots from them are not going to be high quality either, so you can’t expect anything that would rival what you can get from a camera, even a point and shoot camera.