First ripping DVDs is considered illegal even if it is for your own use according to the Digital Copy protection legislation in the USA. An alternative would be to use an analog recording. I use the Hauppauge 1212 HD-PVR Video Capture device
by playing the DVD out of one PC to the 1212 on another PC. This could be from a DVD player to the 1212 as well. Audio can be hooked up digital optical for 5.1 surround sound. There is no perceivable difference in quality.
I've only done a few SD DVDs as most of my movies are recorded from my DVR in HD.
Going the analog route gets around the digital copy law and also produces a smaller file than the storage space used for the whole DVD. I don't get all of the menus and extras unless I record them separately, but I get the movie itself and for me that is all I usually want.
The best part for me is it is completely legal.