I should have said, "Media Player would recognise Cineplayer's decoder".
My version of Vista, Business, does not come with a DVD decoder. In earlier versions of Windows, Media Player, and other DVD players, recognised other DVD decoders and worked just fine.
If you follow Microsoft's misleading information trail for the "No decoder" scenario, you end up at a page which offers to sell you the Cineplayer Codec pack. Er, I thought I had that as a part of the Roxio Suite. Media Player doesn't want to know.
The only reason why I installed Roxio on the new PC was to get the DVD decoder. (Sadly, it does not allow you to install just that, so I had to include most of the package.)
I was like you with Vista. But I needed to build a new PC and didn't want to mess around with Vista in a year or two. In the event, the experience has been mostly fine. I had to turn off the excessively nannying User Account Control. But apart from that, the system has been very stable. All of my software and hardware work.
I did hang back until Vista SP1 was imminent. I installed that yesterday. Like many people, it seems, I lost my sounds. But reinstalling the drivers fixed that.