If you want to copy DVD Video files to your hard disk
like a VCD, then you need to convert it to a VCD format. You can use any DVD Ripper - For example this one -
http://www.dirfile.com/dvd2avi_ripper_free.htm
You can convert your DVD video to avi, or any other format which you prefer. But remember, DVD is the highest quality available. Ripping or converting it to another format will definately result in quality loss, it may be minor or major depending on the format and settings you choose.
Another point - If you copy .vob files to your hard disk, you can view them with PowerDVD or any other media player too.