System freezes when playing DVD in media player

I have done a clean install of Windows 7rc on a Toshiba Satellite laptop. When I try to play a DVD on media player it starts loading and then the system freezes / blacks out. I have to reboot. It sometimes does the same when trying to play video files. Also when I try and run the Windows Experience Index the system again completely freezes as soon as it reaches the test for "Windows Media Decoding". I would appreciate any advice. I have ordered the release version - I hope it is not going to do the same thing.

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