take the advice from a person who had every version of media center since 2002.
it doesn't come with one. now if you have a ati or nvidia card I can tell you the best one to use. avivo and nvidia pure video decoder use hardware instead of software to decode so you will always have a better picture. hardware kick software but by a tenfold. I use to use hardware dvd decoders (real magic. $300.00) before ati and nvidia came out with these.