Correction: Foobar 2000.
I haven’t used WMP in years, didn’t trust them as far back as XP. I use Mplayer for Windows, works quite well and the only file type I ever found that it wouldn’t play was the videos made by my Pentax K-x DSLR I used for a couple of years. IT works fine with the video from the K30 I use now.
http://mplayerhq.hu/design7/news.html