High-end cards, particularly the sort gamers buy, often come with DVD software. I have no idea if it's downloadable or not, though.
If you email Pioneer, BTW, they should be able to direct you to who you can purchase some legit DVD playback software off. It won't be very expensive and it'll be the same as supplied in consumer packages of that drive. The OEM drives don't come with such software, BTW, which is why it isn't for download.
And you *can* get DeCSS for Windows; I have it here somewhere. Doesn't play the VOB files, of course.
Wade.