>>ATI Multimedia Center software supports playing DVDs on PC and even DVD output to attached TV.
>
>I have ATI TV Tuner 7.1. Is some of that good for such a need?

Depends on version. ATI Multimedia Center 7.1 (the one you can download from http://mirror.ati.com/support/drivers/misc/mmc71tvwonder.html)
which is supplied with ATI TV-Wonder card does not contain ATI DVD Player.

See

http://www.ati.com/support/infobase/2874.html

http://search.ati.com/nasearch.asp?rdoCatalog=Driver&Query=ATI+DVD+Player+&DefaultLanguage=16&Catalog=NACustomerServiceSupport&Start=&Total=&Stat=New&go.x=9&go.y=14

I don't have DVD-ROM myself, so I didn't try it.