I find it much easier to put all the trailers from the Microsoft Keynote at GDC intoone big preview post. One stop shopping and all. Check them all out below:

XNA Info
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XNA Games
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Ninja Gaiden 2
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Fable 2 Developer Walkthrough #1
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Fable 2 Developer Walkthrough #2
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Fable 2 Developer Walkthrough #3
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Too Human Sacrifice Cutscene
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