How long does it take to convert a 500 DVD collection into H.264-based MP4 files?

Some years ago I converted all my audio CDs which I own legally into MP3 files because an external hard drive requires less space in my living room and I can search and pick music more easily and listen to the music in my car during my daily commutes. I’m thinking about doing the same with my DVD collection which I also own legally. I have no intention of sharing anything and therefore the effort is legal in my country. Again my shelves are getting crowded and a 500 gigabyte drive doesn’t cost much. But what about the effort of converting everything? How much time does it take? Will my 2006 PC running XP be up to the job?