If you connect the VCR to your computer through a TV tuner type card, such as the one I use called WinFast TV, then you can use your computer like a TV to watch live TV, connect a VCR, and watch the video tapes on your computer. If you get a DVD drive for your computer, you can put a DVD in there and watch it on your computer using the program called Windows Media Player, or RealPlayer, or iTunes, or something else like that. When you use these programs, depending on which one you use, it should work. Using Windows, there should be a button on your keyboard that says somewhere PrintScrn or, if you use a Mac with an external DVD drive or an internal one, depending on how new it is, you can press Command+Shift+3 to take what is called a screenshot of whatever you are viewing at the time. This should work while viewing your movie. In windows, this picture goes to your clipboard after you press "PrintScrn" From there, you can open up Paint, and choose "Paste as new image" from the edit menu. You will need to then save it as an image document so that it can be accessible in the future for editing, viewing, etc. Just like you would with a photo from your digital camera.
With a Mac, the image will be saved to your desktop, but you can put it in your pictures folder under users, then your user name's folder, so that it will then be accessible as part of your iPhoto library. But even if you leave it on the desktop, you can double-click on it and it will open Preview for you. If you need to connect your VCR to your Mac, there should be a cable you can purchase from apple that converts the standard RCA format for VCRs, TVs, DVD players, and the like into a VGA or FireWire format that your Mac will recognise. This information all has to do with the latest G3 iMacs, Powermacs, iBooks, and PowerBooks, through the current models, all have to be running OS X version 10.2.8 or higher. This also refers to Windows PCs from about 700MHz and up, running Windows 2000 through Vista. I hope this helps!!