http://www.smartphonemag.com/forum/topic.asp?TOPIC_ID=19322

Q: How come I don't see any video on my Pocket PC 2002 device? I do hear the soundtrack! A: this is because the Series 8 Pocket Windows Media Player (WMP) on your device only supports Windows Media Video (WMV) 8, which means it won't play the video part of the files that have been encoded with the series 9 of Windows Media Encoder (WME), which has been commonly used in the last 3-4 years. Unfortunately, not even the latest version of series 8, 8.5, which came with the EUU3 (and, therefore, in EUU4) upgrade and was contained by default with late-2002/early-2003 PPC2k2 devices like the iPAQ 545x/Toshi e75x is able to play WMV9 videos (only, as has already been pointed out, WMA9 audio tracks). To eliminate this problem, - upgrade your Pocket PC to WM2003 if possible. (Unfortunately, very few PPC2k2 devices can be upgraded – the (original) Toshiba e75x, the Dell Axim x5's, the Pocket Loox 600, the (English) iPAQ 38xx, the 39xx and the 545x series. Owners of the Asus a600, the iPAQ 1910, the Toshiba e740 and several other, for example, 570-series devices, the iPAQ 36xx/37xx/non-English 38xx, are left out in the cold.) - use another encoder instead of WME. Alternative encoders (particularly XviD/DivX-based ones) a. may offer much better compatibility with other platforms than WME – for example, if you encode your videos into DivX, you'll be able to play them on most of today's standalone DVD players, unlike with WMV videos b. not only offer much broader platform compatibility but also the ability to be reconverted. An XviD/DivX video can always be reconverted/accessed with free tools like VirtualDub, unlike a WM one. c. have much better Pocket PC players than WMP. TCPMP is orders of magnitude better than WMP in almost every respect. (Note that TCPMP is also able to play WMV files.) If you need to know how you can downsample your existing DivX/XviD videos, read this blog entry.