I'm curious if there is a way to decrypt CSS-encrypted DVD's transparently to the user. That is, of course one can use programs like DVD Decrypter or SmartRipper to copy CSS-protected .vob's to hard drive, but what I'm looking for is a driver that allows the protected files to be already seen as unprotected when you open then with any Windows program (basically, CSS decryption on-the-fly). If such program exists, it would be a lower filter driver that installs on an IDE/SCSI device, much like AudioFS (that allows you to see audio tracks on a CD-DA disk as .wav files (instead of .cda) -- which then can be opened and manipulated in a regular manner with any Windows program).
I don't know the specifics of how CSS works, but I know that it has two parts to its decryption key, one of which is stored in an area not normally accessible as a file. That is why programs like DVD Decrypter need to either use ASPI to read raw sectors from the DVD to find a key, or (if ASPI is not available) have to bruteforce the key. Thus, I conclude that if you have direct disk access to the DVD drive (a lower filter driver does), you should have no problems decrypting CSS on the fly -- like any standalone DVD player does.