Seems as if there is a lot of misunderstanding by some about coppying from VHS to DVD (or anything, for that matter)...
Commercial VHS tapes have a protection scheme called "Macrovision". Not all commercial VHS tapes have it, but many, if not most do.
Without getting too technical, Macrovision basically causes the recording device to continually adjust the gain up and down, making the recorded video unplayable.
Macrovision at WikipediaIn order to "beat" this copy protection scheme you need to strip the codes out that macrovision puts on the tapes.
One method is to use an old VCR which does not recognize the Macrovision protection scheme.
Another method is to use a device between the VCR and DVD recorder that strips out the codes.