I bought the 3.0 upgrade and found that the classic Windows Media Player no longer works - it just displays a white "rectangle" I installed the latest WMP (version 11) and while it does display video, if you resize the window, the video portion doesn't resize so you get left with a tiny portion of the video player showing you video and the rest of the window has nothing.
Hmmm, an interesting theory that I'll try....but I'm a little confused --- I thought the whole point of upgrading to 3.0 was so that I'd get DirectX support ---- now you're telling me to disable it?