The folk who responded to your query seemed to have forgotten that it is
perfectly fine to copy DVDs to the HDD if the copies are not burnt to a disc
and the copies are deleted immediately after viewing, so I shall answer your
query myself. The only thing I can offer you is empirical evidence, though.
I have copied around 150 DVD discs to my HDD (no, I am not going to
specify what I do once they are ripped, folks... I know better than that).
Having done so, I can report that with two different NEC ND-3500A drives
doing the ripping for most of those copies there have been almost no
problems whatsoever in the ripping of the DVD discs to the HDD using
DVD Decrypter (can be found via Google). Many of the discs were in
terrible condition since almost all were rental discs.
So, you should have little to no problems. One caveat is that the quality
of commercially produced pressed discs can vary according to which studio
had them manufactured, and you might notice this as well over the course of
time and many rips.
A sidenote: I find that I gain a smoother playback of DVD films if I first
copy them to the HDD, then use an application like PowerDVD to open the
film from the HDD location where I copied the film. So, there are
legitimate uses for copying commercial DVDs to the HDD, and Robin did not
specify that he/she was going to pirate anything, so we should all remember
our manners when folk come here seeking assistance.