One good app is OPlayerHD. You can get a lite version for free (get ads, if I remember correctly). The paid version is $4.99 or so...
It's my main app for opening those oh-so-cute email .wmv attachments that friends send you. You know the ones! So, far, knock on wood - I've had great success with it.
Of course, and as always, YMMV.
Marilyn