Yes, DVDDecrypter still works in Vista. It is seriously outdated as a decryption program however.
If you run into a dvd it can’t handle on its own, I suggest using the free version of DVDFab, called DVDFab HD Decrypter. Found here: http://www.dvdfab.com/free.htm Be aware that as you use the free section of the program, you are using up the trial period of the full program, but the free section will still decrypt and rip dvds for you even after the trial is finished.
A second option is to use AnyDVD. It is my choice for a decryption program and can be used in conjunction with programs like DVDDecrypter or DVDShrink. AnyDVD is not free, though there is a trial for it as well.