An analogy signal going to an analog display can give you a fuzzy image. An analog signal to a digital display cannot. A poor quality analog signal would either not show at all, or show with random corruption, which wouldn't look anything like what the word "fuzzy" describes.
A normal VGA cable under ten feet long or so will not have such a problem.
The only difference you might see between VGA and DVD-D is lower contrast.
Finally, make sure that the port is DVI-I and not DVI-D. The former is either digital or analog, while the latter is digital only. Compare the appearance with the pictures you see here to check.