DVD Remaster Pro is a paid one
Handbrake is a very popular free one.
Some stuff that Handbrake can't decrypt can be handled by Mac the Ripper (only rips, no re-encoding)
/edit; And don't forget to grab MetaX too...I haven't found anything on Windows nearly as good. (It adds all the metadata to the re-encoded file)
Sorry no.
Are you sure they aren't blu-ray or something?
Some DVD's just don't use the 'standard' copy protection. Then you have to get into the more expensive options for decrypting. I don't have any experience with those - all my DVD's ripped just fine. Of course, my DVD collection is mostly older discs, I have stopped collecting movies altogether.