The biggest problem with a lot of the analog to digital solutions out there, like the Pinnacle products, is that the sampling rate sucks. Sampling IS a-to-d conversion; you take an analog input and make numerous, discrete measurements (samples) of that input. The more samples you have, the more accurately you will be able to approximate the original input.
In the case of old video tapes, like Platterman suggested, the best way to copy them is using a DVD recorder. Use the high quality setting. This will give you only 2 hours of recording time, but you'll minimize the effect of copy degredation. You can then remaster the videos using a product like Adobe Premier Pro.
For photos... pretty much any modern flatbed scanner will provide more than sufficient resolution for a high quality scan (aim for a minimum of 10 megapixels). Then you can clean up the photo using Photoshop, just make sure to leave the original scanned image unchanged so you always have a pure source document to work with.