If it is a movie, you can use DVD shrink. DVD shrink will allow you to rip a dual layer DVD to your hard drive, compressing it enough to fit on a regular DVD. You can also control this compression, edit unneeded audio streams, re-author your DVD, but compression is compression, and it is a loss in the original DVD quality. (This is why I usually remove the menus and unneeded audio streams. Usually cuts it down to 80% quality of the original.) If you absolutely need untampered copies, you will either need to purchase more expensive Dual Layer DVD's or use the method that DanB suggested, also depending on whether this is data or not. WinRar will work for data, but for a DVD movie, use what DanB suggested. He knows his stuff.