Before you copy the DVD play it on the PC, this will bypass any security on the DVD.
Some dvd's are dual layered, that a 9.4gig disc, if you shrink it to fit a normal 4.7gig disc the quality will be real bad. If you have a dual layered burner use the bigger disc they are peanuts now as regards to price.
Most of the 9.4 dvd's have all the extras like out takes and behind the scenes shots and what not. Obviously if it's just the film you whant to back up for safe keeping
look for dvdecrypter (it's out there Moulder). This will let you strip out the film you want without the rest of the junk. The film you are left with will nine times out of ten fit on a 4.7 disc with no compression needed.
You dont want to compress more that 15 to 20% other wise quality suffers.
Remember to play first though.
PM sent