DVDShrink has not been updated since 2004. It is no longer an effective decryption program for many newer dvds that have advanced protection added to them.
You should get the free trial for DVDFab. While the trial lasts (30 days), you will be able to decrypt, rip and compress movies with it. Once the trial ends, there is still a free section within DVDFab that you can use to decrypt and rip movies. It is called DVDFab HD Decrypter. Once you use it to rip the movie onto the hard drive, you can then use DVDShrink to compress if that is necessary.
The only caveat to using DVDFab HD Decrypter is that it will lag behind the commercial DVDFab by 6 to 8 weeks on updates. Still, it is the nearest thing we have to a free decryption program for dvds that is reasonably up to date.
You can find DVDFab here: www.dvdfab.com